40
8x5=40
10x4=40
Hope this helps
17) 
18) 
19) 
20) 
Step-by-step explanation:
17) The difference between a number and 8 is 11
Let number = x
then the equation will be:

Solving:


18) Nine less than a number is five.
Let number = x
then the equation will be:

Solving:

19) Seven is equal to a number plus 6
Let number = x
then the equation will be:

Solving:

20) The sum of a number and -4 is -18
Let number = x
then the equation will be:

solving:

Keywords: Algebraic Expressions
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Option 4 is correct i.e. <span>The volume of the box is increasing at a rate of 192 cm^3/min.
</span>Given : Volume of the rectangular box = x²h
where x is edge and h is height.
The edge and the height are varying with time, therefore, we write,x = x(t)
h = h(t)
dh/dt = -3 and we shall calculate when x = 4, dx/dt = 2 and when h=15
V = x²h dV/dt = (2x × dx/dt × h) + (x² × dh/dt) dV/dt = 2×4×2×15 + (4)^2 ×(-3) dV/dt = 240 - 48
dV/dt = 192
Because dV/dt is positive, hence the volume is increasing