$$2n+n\left(1\times 2+1\right)+2n+2.8=7$$
Multiply $1$ and $2$ to get $2$.$$2n+n\left(2+1\right)+2n+2.8=7$$
Add $2$ and $1$ to get $3$.$$2n+n\times 3+2n+2.8=7$$
Combine $2n$ and $n\times 3$ to get $5n$.$$5n+2n+2.8=7$$
Combine $5n$ and $2n$ to get $7n$.$$7n+2.8=7$$
Subtract $2.8$ from both sides.$$7n=7-2.8$$
Subtract $2.8$ from $7$ to get $4.2$.$$7n=4.2$$
Divide both sides by $7$.$$n=\frac{4.2}{7}$$
Expand $\frac{4.2}{7}$ by multiplying both numerator and the denominator by $10$.$$n=\frac{42}{70}$$
Reduce the fraction $\frac{42}{70}$ to lowest terms by extracting and canceling out $14$.$$n=\frac{3}{5}$$