Hello!
The distributive property is going to be very important in this. It states that when you have a variable multiplied by a set of parenthesis, you distribute that variable inside the parenthesis (as long as the operations inside the parenthesis are addition or subtraction). For example, 2(x + 4), you can distribute the 2 to x and 4, to get 2x + 2(4).
Now, distribute t to inside the parenthesis.
T(r + s) = rs
Tr + Ts = rs
Now, move everything with an r in it to the right side.
Tr + Ts = rs
Ts = rs - Tr
Use the opposite of the distributive property, to extract r from the right side.
Ts = rs - Tr
Ts = r (s - T)
And divide both sides by s - T to isolate the r.
Ts = r (s - T)
[tex]\frac{Ts}{s-T}[/tex] = r
Hope this helps!
