4r+3=r+21

How do I do this?

You first:

4r+3-3=r+21-3

4r=r+18

4r-r=r-r+18

3r=18

3r/3=18/3

r=6

remember that what you do in one side, do it in the other

Simplify: 4r + 3 = r + 21, then reorder the terms: 3 + 4r = r + 21.

Reorder the terms 3 + 4r = 21 + r. Solve: 3 + 4r = 21 + r.

Move all terms containing r to the left, all other terms to the right.

Solving for variable 'r'.

Add '-1r' to each side of the equation. 3 + 4r + - 1r = 21 + r + - 1r.

Combine like terms: 4r + - 1r = 3r 3 + 3r = 21 + r + - 1r

Combine like terms: r + - 1r = 0 3 + 3r = 21 + 0 3 + 3r = 21

Add '-3' to each side of the equation. 3 + - 3 + 3r = 21 + - 3

Combine like terms: 3 + - 3 = 0 0 + 3r = 21 + - 3 3r = 21 + - 3

Combine like terms: 21 + - 3 = 18 3r = 18

Divide each side by '3'. r = 6 Simplifying r = 6