You have two angles in the triangle so you can find the third: A=180-(68+24)=180-92=88 degrees.
Now you can use the sine rule to find the side: AC/sinB=AB/sinC=BC/sinA. So we can use BC/sinA=AC/sinB.
BC=ACsinA/sinB=15sin88/sin68=15*0.9994/0.9272=16.17cm to 2 dec places.