You probably made a typing error in writing s = -3 and wrote s - = 3 instead.
The given expression is:
[tex]-3|15-s|+ 2^{3} \\ \\
-3|15-s|+8
[/tex]
Substituting the given value of s in the previous equation, we get:
[tex]-3|15-(-3)|+8 \\ \\
=-3|15+3|+8 \\ \\
=-3|18|+8 \\ \\
=-54+8 = -46[/tex]
Thus the value of given expression becomes -46 for s = -3
