$$\frac{15}{18}-\frac{8}{18}-\left(-2\right)$$
Since $\frac{15}{18}$ and $\frac{8}{18}$ have the same denominator, subtract them by subtracting their numerators.$$\frac{15-8}{18}-\left(-2\right)$$
Subtract $8$ from $15$ to get $7$.$$\frac{7}{18}-\left(-2\right)$$
The opposite of $-2$ is $2$.$$\frac{7}{18}+2$$
Convert $2$ to fraction $\frac{36}{18}$.$$\frac{7}{18}+\frac{36}{18}$$
Since $\frac{7}{18}$ and $\frac{36}{18}$ have the same denominator, add them by adding their numerators.$$\frac{7+36}{18}$$
Add $7$ and $36$ to get $43$.$$\frac{43}{18}$$