1: make x the subject: 4(x+y) = z
2: make b the subject: ab + cd = e

Explanation:

(1) Making x the subject:

To make x the subject of original expression, we send the x to the left side of expression and all of the other components to the right side of expression.

The detail procedure is described as following:

Apply associate property:

<=>

Send 4y to the right side (the sign of 4y must be changed from positive to negative):

<=>

Divide both sides by 4:

<=>

(2) Make b the subject: ,  applying the similar procedure in part (1):

Send to the right side (the sign of

<=>

Divide both sides by :

<=>

Hope this helps!

:)