Find the follow of x 10/4=15/x

Simplify 10/4 to 5/2

Then multiply both by x, Then simplify 5/2 to 5x/2 and you get 5x/2 = 15

After that multiply by 2, 15 x 2 to 30

Then divide both by 5, x = 30/5

finally 30/5 = 6

so your answer is 6