Plz me with these 4 questions 15-18 about pythagorean theorem.

A^2+b^2=c^2
the longest side (side oposite the right angle) =c so
15.
c=7.3
a=3.6 ( can be b, just assign a leter)
3.6^2+b^2=7.3^2
expand
12.96+b^2=53.29
subtract 12.96 from both sides
b^2=40.33
square root both sides
b=6.35

16.
c=11
a=3.9
3.9^2+b^2=11^2
15.21+b^2=121
subtract 15.21 from both sides
b^2=105.79
square root both sides
b=10.29

17.
c=9.9
a=6.5
6.5^2+b^2=9.9^2
42.25+b^2=98.01
subtract 42.25 from both sides
b^2=55.76
square root both sides
b=7.47

18. 
c=13.3
a=9.7
9.7^2+b^2=13.3^2
94.09+b^2=176.89
subtract 94.09 from both sides
b^2=82.8
squar root both sides
b=9.1