Can someone please explain to me how to do this problem step-by-step

**Solve for b: H=5/3(a+2ab)**

I know the answer is b=3H-5a/10

However, I'm just unsure how to get there, more specifically how H became 3H.

More, more specifically I don't know how to multiply the fraction with the equation... for the right side I know I convert the a and 2ab into fractions by giving them the same denominator as 5/3 (i.e. 5 * a/3 + 2ab/3)

..But, how did 3 get multiplied with H.. shouldn't it be 5/3*H = 5/3 * H/3? (why is H getting multiplied with the denominator??)

please explain to me how this works

thanks!