Answer:
$2.50
Explanation:
Let's set up a proportion using the following setup.
price / pens = price / pens
We know that it costs $4.00 for 8 pens.
$4.00 / 8 pens = price / pens
We don't know how much it costs for 5 pens. Therefore, we can say it costs $x for 5 pens.
$4.00 / 8 pens = $x / 5 pens
4/8=x/5
We want to solve for x (the cost for 5 pens). Therefore, we must get x by itself on one side of the equation. x is being divided by 5. The inverse of division is multiplication, so multiply both sides of the equation by 5.
5*(4/8)=(x/5)*5
5*(4/8)=x
5*0.5=x
2.5=x
x= $2.50
Ivan should pay $2.50 for 5 pens.