Answer:
r = P -t -s
Step-by-step explanation:
This is a one-step linear equation in r. Subtract the terms that don't contain r:
P = r + t + s . . . . . . . . . . given
The terms on the right that don't include r are (t+s). We want to subtract that to get r by itself.
P -(t+s) = r +(t+s) -(t+s) . . . subtract (t+s)
P -t -s = r . . . . . . . . . . . . . . simplify
r = P - t - s
