Question 165382
A+B+C=57  A=2B  and C=B+7  so substituting A=2B and C=B+7 into the 1st equation we get (2B)+B+(B+7)=57  so 4B=50   B=12.5  so A=2(12.5)=25 and C=12.5+7=19.5

So sides are 12.5,19.5,25 in length