Mrs.Carter bought 7 dry erase markers for $40. How much would 20 markers cost ?

40/7 = x/20

Solve for x.

114.2

To determine the cost of 20 markers, we can set up a proportion using the given information. We know that 7 markers cost $40. Let's set up the proportion:

7 markers cost $40
x markers cost $?

The proportion can be written as 7/40 = x/20.

To find the value of x, we can cross-multiply:

7 * 20 = 40 * x

Simplifying further:

140 = 40x

Finally, we can solve for x by dividing both sides of the equation by 40:

x = 140/40 = $3.50

Hence, 20 markers would cost $3.50.