Answer:
That depends on which operations you want to do first. The order of operations affect to outcome of the equation.
In this case:
15 - (3 x 4) + 9 = 12
The cost of large pizza is $24.62, a small pizza has an 8-in. diameter a large pizza has a 15-in. diameter the pizzeria charges the same price per square inch for both pizzas and the small pizza cost $7.
Step-by-step explanation:
The given is,
A small pizza has an 8-inches in diameter
A large pizza has a 15-inches in Diameter
The small pizza cost $7
Step:1
Area of smaller pizza,
...................................(1)
Where, r - Radius of small pizza
From given, 

r = 4 inches
Equation (1),

( ∵
=3.14 )
Square inches
Step:2
Area of smaller pizza,
...................................(1)
Where, r - Radius of small pizza
From given, 

r = 7.5 inches
Equation (1),

( ∵
=3.14 )
Square inches
Step:3
Cost of pizza per square meter,


= $ 0.1393 per square meter
× 

= $24.62
Result:
The cost of large pizza is $24.62, a small pizza has an 8-in. diameter a large pizza has a 15-in. diameter the pizzeria charges the same price per square inch for both pizzas and the small pizza cost $7.
i can not give the answer unless you still cannot find it after these steps but I have steps that might help
1. Set the matrix (must be square).
2. Reduce this matrix to row echelon form using elementary row operations so that all the elements below diagonal are zero.
3. Multiply the main diagonal elements of the matrix - determinant is calculated.