Lunch Time

$20$ % of $50.50$ is = $\frac{50.50 \times 20}{100}=10.1$

so,he will spend= $50.50+10.10=60.6$

We can write $20\%$ as $0.2$ to get that $20\%$ of something is same as $0.2x$ when $x$ is whole thing.

In this case $x = 50.5$ .

$0.2(50.5) = 10.1$ ( $10$ dollars and $10$ cents)

$50.5 + 10.1 = 60.6$ Tim spent $60$ dollars $60$ cents.

If you wanted to write all that in one "formula", you would have: $50.5 + 0.2(50.5)$

Or even more elegantly: $1.2(50.5)$