Simplify $7n^2+5n^2-2n^2$7n2+5n2−2n2.

Simplify $8n^2+5n\times7n$8n2+5n×7n.

Simplify $7n\times8n-4n^2$7n×8n−4n2.

Simplify $2n^2+8n^2\div2$2n2+8n2÷2.