Solve::naqs: <<1>> is not a quantified system of equations and inequalities

Questions
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1

Solve[ C2 == 00 && C1 == 0 &&
0 == -7293.097904399998` + 6.6` C1 + C2 + 21.779999999999998` M1 +
47.916` R10 &&
0 == -116689.56647039996` + 13.2` C1 + C2 + 87.11999999999999` M1 +
383.328` R10 + 47.916` R11 &&
0 == -590740.9302563999` + 19.8` C1 + C2 + 196.02` M1 +
1293.732` R10 - 47.916000000000025` R11 +
47.916000000000025` R12 &&
0 == -1.8670330635263994`^6 + 26.4` C1 + C2 +
348.47999999999996` M1 + 3066.624` R10 +
1293.7319999999995` R11 + 383.328` R12 +
47.915999999999954` R13 &&
0 == -4.55818619025`^6 + 33 C1 + C2 + 544.5 M1 + 5989.5 R10 +
3066.624` R11 + 1293.732` R12 + 383.328` R13 +
47.916000000000025` R15 &&
0 == -9.451854884102399`^6 + 39.6` C1 + C2 + 784.08` M1 +
10349.856` R10 + 5989.5` R11 + 3066.6240000000007` R12 +
1293.732` R13 + 383.3280000000002` R15 +
47.916000000000025` R17 &&
0 == -1.75107280684644`^7 + 46.2` C1 + C2 + 1067.22` M1 +
16435.188000000002` R10 + 10349.856` R11 + 5989.5` R12 +
3066.6240000000007` R13 + 1293.7320000000009` R15 +
383.3280000000002` R17 + 47.916000000000025` R18 &&
0 == -2.987252901642239`^7 + 52.8` C1 + C2 +
1393.9199999999998` M1 + 24532.992` R10 +
16435.187999999995` R11 + 10349.855999999996` R12 + 5989.5` R13 +
3066.624` R15 + 1293.7319999999995` R17 +
383.32799999999963` R18 + 47.91599999999987` R19 &&
0 == -4.7946755305453904`^7 + 59.43` C1 + C2 + 1765.96245` M1 +
1765.96245` M2 + 34983.7161345` R10 + 24574.8333645` R11 +
16467.225394500005` R12 + 10373.396224499997` R13 +
6005.8498545` R15 + 3077.0902845` R17 + 1299.6215144999996` R18 +
385.9475444999997` R19 &&
0 == -5717.0124` + R10 + R11 + R12 + R13 + R15 + R17 + R18 + R19 +
R20 + R21 &&
0 == -3.227107878543087`*^6 + 59.43` C1 + C2 + 59.43` M1 +
1765.96245` R10 + 1395.50445` R11 + 1068.6064500000002` R12 +
785.2684499999998` R13 + 545.49045` R15 + 349.27245` R17 +
196.61444999999998` R18 +
87.51644999999996` R19 &&

 **-169795.26828` - M2 + 6.6` R11 + 
   13.2` R12 + 19.8` R13 + 26.4` R15 + 33 R17 + 39.6` R18 + 
   46.2` R19 + 52.8` R20 + 59.4` R21**


]
2

Like the message states, they are not all equations (the final one has head Plus). This is the sort of thing that should be checked before posting to an open forum.

3

Solve[{0 == x + 2y + 2z + t, 0 == 2x + y + 2t, 0 == 2*x + y - t,
0 == x + y - t} {x, y, z, t}]
Why it does not work?

4

A comma is missing

Solve[{0 == x + 2 y + 2 z + t, 0 == 2 x + y + 2 t, 0 == 2*x + y - t, 0 == x + y - t}, {x, y, z, t}]
(* {{x -> 0, y -> 0, z -> 0, t -> 0}} *)