1. The problem is to find the value of the expression $42.25 + 9$. 2. The formula used here is simple addition: $a + b = c$, where $a = 42.25$ and $b = 9$. 3. Add the two numbers: $$42.25 + 9 = 51.25$$ 4. Therefore, the value of the expression is $51.25$.