Multiply (3b 2+ 4b + 8)(-2b 2+ b + 10).

-30b^2+76b+80
Explanation:
Multiply the second parenthesis by each term from the first parenthesis:
3b•2(-2•2+b+10)+4b•(-2b•2+b+10)+8(-2b•2+b+10)
Then distribute 3b•2 through the parenthesis
-24b^2+6b^2+60b+4b•(-2b•2+b+10)+8(-2b•2+b+10)
Then collect like terms
-30b^2+60b+40b-32b+8b+80
Collect like terms=
-30b+76b+80

21/2 or 5/2

She will need 5/8 bags for each square yard.