How do you simplify  8(5+x) -3x(x-3)?

Apr 20, 2016

$= - 3 {x}^{2} + 17 x + 40$
To simplify it (and therefore solve it), you'll need to know the distributive property, which is $a \left(b + c\right) = a b + a c$ If you want further explanation of this, please say so
$8 \left(5 + x\right) - 3 x \left(x - 3\right) = 8 \left(5\right) + 8 \left(x\right) - 3 x \left(x\right) - 3 x \left(- 3\right)$
$= 40 + 8 x - 3 {x}^{2} + 9 x$
$= - 3 {x}^{2} + 17 x + 40$