To determine which expression is true, we have to do the operations and check that on both sides of the equation is the same number.
Then, in this case we have:
[tex]\begin{gathered} a)9+4=13 \\ 17-4=13 \\ b)8+7=15 \\ 14+3=17 \\ c)19-8=11 \\ d)5+8=13 \\ 20-7=13 \end{gathered}[/tex]notice that the only option that don't match is b, therefore, the option b is not true
