Answer:
21
ctto JBarnum
Step-by-step explanation:
P+11=(1/2)(P-13)^2
P+11=(1/2)(P^2-26p+169)
2(P+11)=(1/2)(2)(P^2-26p+169)
2P+22=P^2-26p+169
0=P^2-28p+147 ( -7 and -21)
(P-7)(P-21)=0
P=7,21 (cant be 7 as 13 years from 7 is negative so peter is 21)
checking:
21+11=32
32=(1/2)(21-13)^2
32=(1/2)(8)^2
32=(1/2)64
32=32
correct
The answer should be the third one
