x (a + 2) = 7
First let's multiply out the brackets on the left side of the equation.
x (a + 2) --> Multiply everything inside the brackets by x.
xa + 2x = 7
Now, both elements of the left-hand side of the equation contain x, so we can divide both sides of the equation by x.
xa + 2x = 7
a + 2 = 7/x
To find a now, just subtract 2 from both sides.
a = 7/x - 2