We can use difference of squares for the first equation to get:
\((a+b)(a-b) = 10\)
Then we can substitute our second equation in to get:
\((a+b)(2)=10\)
Dividing both sides by 2, we get:
\(a+b = 5\)
remember that \(a^2 - b^2\) can be factorized into \((a+b)(a-b)\)
