Question 116403
A^2+B^2=C^2
X^2+(X+3)^2=15^2
X^2+X^2+6X+9=225
2X^2+6X+9-225=0
2X^2+6X-216=0
2(X^2+3X-108)=0
2(X+12)(X-9)=0
X-9=0
X=9 ANSWER FOR 1 SIDE 
9*2+B^2=225
81+B^2=225
B^2=225-81
B^2=144
B=SQRT144
B=12 ANSWER FOR THE OTHER SIDE.