Answer:
x=10.04
Explanation:
let the triangle sides to be ABC, given <A=90, <B=42 &<C=?
find angle C first
<A+<B+<C=180
90+42+<C=180
<C=180-132
<C=42°
Now use sine rule to find the value of X
a/sinA =c/sinC. where, small letters is equal to sides and capital letters is equal to angles. a=15. c=x
A=90. C=42
15/sin90°=x/sin42°
cross multiply
15*sin42°=x*sin90°
make x subject of the formula
x=(15*sin42°)/sin90°
x=10.04