You must maintain a minimum balance of $50

a.

b.

Explanation:

a. For the first situation, the goal is to make sure that a minimum amount of $50 (balance ≥ 50) is left on the account after withdrawing "n" $20 bills from

an initial $280 (balance = 280 - 20n). The inequality can be modeled and solved as follows:

Since the problem deals with $20 bills, only whole quantities should be considered and then, the inequality should be written as:

b. This situation is very similar to the previous one but it has an additional $2.50 fee for each $20 bill withdrawn (balance = 280 - n(20+2.50)). The inequality can be modeled as follows

Once again, only whole quantities are considered, so the inequality yields:

Step-by-step explanation:

the system of inequalities is

step-by-step explanation:

step 1

find the equation of the dashed line

we have the points

(0,0) and (3,1)

the line passes through the origin, so, is a direct variation

find the slope

the equation of the dashed line is

the solution of the inequality a s the shaded area above the dashed line

therefore

the equation of the inequality a is

step 2

find the equation of the solid line

we have the points

(4,0) and (0,4)

find the slope

the equation of the solid line is

the solution of the inequality b s the shaded area below the solid line

therefore

the equation of the inequality b is

step 3

the system of inequalities is

b. 1.25 hr

step-by-step explanation:

if you have a constant speed of 60 mph, then you have a ratio between 60 mi. to 1 hr. dividing both sides by 60 we get the ratio

1 mi. to

then mult. both sides by 75 we get the ratio

75 mi. to

simplifying we get

75 mi. to

or 1.25 hr.