Answer:
x = 60
Step-by-step explanation:
Direct variation is of the form
y= kxz
We know x =40 and y =10 and z= 20
10 = k * 40 * 20
10 = k * 800
Divide each side by 800
10/800 = k
1/80 = k
The equation becomes
y = 1/80 xz
Let y = 30 and z = 40 and find x
30 = 1/80 * x * 40
30= 40/80 x
30 = 1/2x
Multiply each side by 2
2 * 30 = 2 * 1/2 x
60 = x
