Answer
a=8
Work Step by Step
Given that triangle is right angle triangle where b=6 and c=10
and a 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,
$a^{2}$+$6^{2}$=$10^{2}$
$a^{2}$+36=100
$a^{2}$=64
$a$=$\sqrt 64$=8