Theo made a donation to a charity. His grandfather agreed to add $4.00 to Theo's donation amount and then donate half of that sum. Theo's grandfather donated $4.25. Write and solve an equation to find the amount of Theo's donation

So you have to solve for "donation" - so let's call that X. And the things we know are what the grandfather donated, as a function - meaning based upon - Theo's donation. We'll call that Y.

So Y is equal to 1/2 of $4 plus Theo's donation ... 0.5 * (x+4).

So ... 4.25 = 0.5 (X+4), solving for X

4.25=0.5x + 2

-2 - 2

2.25=0.5x - divide each side by 0.5 to get x alone.

x = 4.50

Plugging back in:

(4.50 + 4.00) * 0.5 = 4.25!