Can someone tell me how to do number 15 please!!!

Answer:
x = 90
c = 11
d = 11
Step-by-step explanation:
For this, we just need to use algebra to solve for x.
(x / 3) - 4 = 26 | First we add 4 to both sides
x / 3 = 30 | Then we multiply both sides by 3
x = 90.
For the others, it's the same.
-8 + 10c = 102 | Subtract -8 from both sides, or add 8
10c = 110 | Divide both sides by 10
c = 11
2.5d + 7.5 = 20 | Subtract 7.5 from both sides
2.5d = 27.5 | Divide both sides by 2.5
d = 11