perhatikan gambar berikut nilai x sama dg?

Karena segitiga sebangun misal,
9 : ( x + 10 ) = 8 : 10
90 = 8 ( x + 10 )
90 = 8x + 80
8x = 90 - 80
8x = 10
x = 10/8. = 1 1/4