aaaaaaaaaada yang bisaa?

doa dulu ya baru dikerjakan ya tugasnya

[tex] \frac{12+x}{9} [/tex] = [tex] \frac{20}{12} [/tex]
9 x 20 = 12 (12+x)
180 = 144 + 12x
180 - 144 = 12x
36 = 12x
[tex] \frac{36}{12} [/tex] = x
3 = x
x = 3