Hello!

8c - 3c + 3 = 13
Begin by combining like terms:
5c + 3 = 13
Subtract 3 from both sides:
5c + 3 - 3 = 13 - 3
5c = 10
Divide both sides by 5:
5c/5 = 10/5
c = 2.
7 the awnser is 7 ok(kkkkk
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The height of the water tank is 6.
L x W x H = V (volume)
15 x 10 x 6 = 900 cubic feet