Posted by nmdna on .
y varies directly with x. When y = 20, x = 50. Find x when y = 36.

algebra 
Reiny,
y varies directly with x > y = kx , where k is a constant
20 = k(50
k = 2/5
y = (2/5)x
when y = 36
36 = (2/5)x
2x = 180
x = 90
or ... use a proportion
x/50 = 36/20
x = 50(36)/20 = 90