Question

What is 7 times the sum of a squared and b minus 4 times the sum of a squared and b

Answer 1

The sum of a squared and b is given by
$a^2+b$

7 times the sum of a squared and b is given by
$7(a^2+b)$
while 4 times the sum of a squared and b is given by
$4(a^2+b)$

Therefore, 7 times the sum of a squared and b minus 4 times the sum of a squared and b is given by

$7(a^2+b)-4(a^2+b)=3(a^2+b)$