Answer
The cost of Madden NFL 13 is \$17.
The cost of Call of Duty:Black Ops 2 is \$30.
Work Step by Step
Let $m$ be the cost of Madden NFL 13.
The cost of Call of Duty:Black Ops 2 is $m+13$.
$m+(m+13)=47$ $\longrightarrow$combine like terms
$2m+13=47$ $\longrightarrow$addition property
$2m+13-13=47-13$ $\longrightarrow$simplify
$2m=34$ $\longrightarrow$multiplication property
$2m\div2=34\div2$ $\longrightarrow$simplify
$m=17$
$m+13=17+13=30$
