The expression that could best describe the statement would be " 40 n + 20

260.
1) Perimeter=2length+2width
This is the formula for finding the perimeter of a rectangle
2) Density=mass/volume
The “Quotient” is the answer to a division problem (like how the “sum” is the answer to an addition problem) which is why we know to divide mass and volume
3) Force = mass*acceleration
The “product” is the answer to a multiplication problem which is why we know to multiply mass and acceleration
4) surface area = 6*L^2
The formula used to calculate the area of a square is L^2. The problem tells us that surface area is the sum of all the faces of a 3D shape. Because there are 6 sides on a cube, we multiply L^2 by 6.
Hope this helps!
A fact family is basically just different equations with the same numbers getting the same/different numbers as answers you might say...
this will make more sense:
5x8=40
8x5=40
40/8=5
40/5=8