#### Answer

b=3.87

#### Work Step by Step

Given that triangle is right angle triangle where a=7 and c=8
and b has to be found
formula for finding hypoteneus of right andle triangle is $a^{2}$+$b^{2}$=$c^{2}$
so after putting values of a and b,
$7^{2}$+$b^{2}$=$8^{2}$
49+$b^{2}$=64
$b^{2}$=15
b=$\sqrt 15$=3.87