Question

Solve for the indicated variable. Include all of your work in your answer. Submit your solution. P = 3r + 2s; for s.

Answer 1

Given

P = 3r + 2s

Find

the corresponding equation for s

Solution

First of all, look at how this is evaluated in terms of what happens to a value for s.

1. s is multiplied by 2
2. 3r is added to that product

To solve for s, you undo these operations in reverse order. The "undo" for addition is adding the opposite. The "undo" for multiplication is division (or multiplication by the reciprocal).

... P = 3r + 2s . . . . . . starting equation

... P - 3r = 2s . . . . . . -3r is added to both sides to undo addition of 3r

... (P -3r)/2 = s . . . . . both sides are divided by 2 to undo the multiplication

Note that the division is of everything on both sides of the equation. That is why we need to add parentheses around the expression that was on the left—so the whole thing gets divided by 2.

Your solution is ...

... s = (P - 3r)/2