matematika kelas 9. tolong dengan cara ya

A(3,-1), B (1,0)
x1,y1. x2,y2

m = Y2-y1 / X2-x1
= 0-(-1)/ 1-3
= -1/2

B(1,0) C (5,x)
x1,y1. x2,y2

m = y2-y1/x2-x1
-1/2 = x-0/ 5-1
-1/2 = x /4
__________. 4
-2 = x
A