12x^2y=1/28*3x*h

I assume this is.....

12x^2y= (1/28 )*3x*h       multiply both sides by 28 and divide by 3x

[(28)(12)x^2 y ] / [3x ]   = h     simplify

[(28)(12)/(3)] * [ x^2 / x] * y = h

[112 x] / y =  h