Question 107118
Let a=x+20, b=x, c=100
a^2+b^2=c^2
(x+20)^2+x^2=100^2
x^2+40x+400+x^2-100^2=0
2x^2+40x+400-10000=0
2x^2+40x-9600=0
2(x^2+20x-4800)=0
2(x-60)(x+80)=0
x=-80 is not an answer. (negative)
x=60 mi (car)
x+20=80 mi (train)
Always check:
60^2+80^2=100^2
3600+6400=10000 true
Ed