y = -5
y = 8
x = 5.y.z so 5.10.12 = 600
m = 24
y = kx: 10 = 37k so k = 10/37 and y = 10x/37
We write y=kx since y varies directly as x. Now we know if x is 5, y is 10. so we write 10=5k so k=2
The answer is x=10. If: x=20 y=8 z=4 then: y=8/2=4 z=4*2=8 since x varies directly with y, meaning whatever happens to y, happens to x, so if y was divided by 2, then x should be divided by 2. After all, the inverse of division is multiplication.
x = 75
y = x/k so 15 = 6/k making k = 0.4. when x = 10 y = 10/0.4 ie 25 alternatively y/x = k ie 15/6 = k so k = 2.5; y/10 = 2.5 making y = 25.