Will give brainliest for right answer!

This is a system of equations.  We solve it by setting it up so that when we add the two equations together, one of the variables will cancel out.  We can do this by multiplying the bottom equation by 3.  This will make our system of equations equal:

3a + b + 225
-3a + 3b = 75

Now we add these two equations together, because the a terms will cancel out.

4b = 300.

We can find what b is by dividing both sides by 4.

b = 75

Next, we plug in b in one of the equations and solve for a.  You can use either equation, but I will use the second.

75 - a = 25

Subtract 25 from both sides and add a to both sides:

a = 50

So, the first option is correct.  A = 50 and b = 75.