Question 399504
Let x=sum of the ages of Kim and Sue, j=age of Janet.
j^2=x^2+400
j=x+10
.
(x+10)^2=x^2+400 Substitute x+10 fo j.
x^2+20x+100=x^2+400
20x=300
x=15
j=25
.
(25+15)^2
=40^2
=1600 the square of the sum of the ages of Janet, Kim and Sue. 
.
Ed