Alejandro solved the equation 5(7x^2-2)-8=3. he wrote 5(7x^2-2)=11 as his first step. which property justifies his first step?

The addition property of equality. It says that if you add the same number to each side of the equation, the two sides of the equation will be equal. In this case, the number 8 was added to each side.

Hope this helps :)