7y + 5y - 8y × 9y

To simplify the expression 7y + 5y - 8y × 9y, we first need to perform the multiplication before addition and subtraction.

8y × 9y = 72y^2

Now, the expression becomes:

7y + 5y - 72y^2

Combining like terms:

12y - 72y^2

So, the simplified expression is 12y - 72y^2.

7y + 5y - 8y × 9y

= 7y + 5y - 72y^2

= (7y - 72y^2) + 5y

= -72y^2 + 12y