Answer
$5x^{2}+53x+72$
Work Step by Step
$(x+9)(5x+8)=$
$...$distribute the second factor, $(5x+8)$.
$=x(5x+8)+9(5x+8)\qquad$...distribute $x$.
$=5x^{2}+8x+9(5x+8)\qquad$...distribute $9$.
$=5x^{2}+8x+45x+72\qquad$...gather like terms.
=$5x^{2}+53x+72$
