5n + 2n + 6 = 4n - 21

5n+2n+6=4n-21 group like terms on left side

7n+6=4n-21subtract 6 from both sides

7n=4n-27 subtract 4n from both sides

3n=27 divide both sides by 3

n=9

add them

step-by-step explanation:

idk you did not give the options or numbers so you cant solve it

so the rectangle is 80cm (area)

now to find the area of a triangle.

base times height.

4 times 8.

your answer is 96cm.

hope this .