5a + (67-a)+ 76 = a
Open up the parenthesis
5a + 67 - a + 76 = a
Rearrange the terms
5a - a + 76 + 76 = a
Add like terms
4a + 143 = a
Subtract a on both sides
4a - a + 143 = 0
Simplify
3a + 143 = 0
Subtract 143 on both sides
3a = -143
Divide 3 on both sides
a = 47.6666666667
And for your second question, 2 + 2 = 4
