#### Answer

(5r+2)($4r^{2}$+3)

#### Work Step by Step

$20r^{3}$+$8r^{2}$+15r+6.Factor out:
You have four terms so group the first two and last two terms:
($20r^{3}$+$8r^{2}$)+(15r+6.)
The GCF for the first group is $4r^{2}$ and for the second group is 3:
$4r^{2}$(5r+2)+3(5r+2)
You have 5r+2 in common so group it by itself:
(5r+2)($4r^{2}$+3)