Question 640396
altitude = x say
base=x+10
then area=x[x+10]----1
new base =x+10+5=x+15
& altitude=x-2
area=[x-2][x+15] ---2
but x[x+10]=[x-2][x+15]
or x^2+10x=x^2+13x-30
or 3x=30
or x=10=altitude
& base=20
ans