AD = AB
AD = 2r+8
AB = 5r-13
we need to find the value of r to find the total length
so 2r+8 = 5r-13
subtract 2r from each side:
8 = 3r -13
add 13 to each side:
21 = 3r
divide both sides by 3
r = 21 / 3 = 7
r=7
now we know r, so replace r with 7 in the equation for AD
AD = 2r+8 = 2(7) +8 = 14 +8 = 22
the answer is D. 22
