At a supermarket , monica paid 3.20 for 2 pounds of apples and 2 pounds of oranges, while sarah paid 4.40 for 2 pounds of apples and 4 pounds of oranges. at these rates, what is the cost , in dollars, for 3 pounds of oranges?

The cost , in dollars, for 3 pounds of oranges is 1.8

Solution:

Given that Monica paid 3.20 for 2 pounds of apples and 2 pounds of oranges

Sarah paid 4.40 for 2 pounds of apples and 4 pounds of oranges.

Let the cost of orange per pound = x  

Let the cost of apple per pound = y  

Therefore, we can frame an equation as follows for Monica and Sarah:

In Monica’s case:  

2x + 2y = 3.20  

Hence x + y = 1.6 eqn 1

In Sarah’s case:  

4x + 2y = 4.40  

Hence 2x + y = 2.2

y = 2.2 -2x – eqn 2

Substitute eqn 2 in eqn 1 we get,

x + 2.2 -2x = 1.6

-x = 1.6-2.2 = -0.6

x = 0.6

Substituting the value of “x” in eqn 2 we get the value of “y” as 1

Thus the cost of orange per pound is 0.6

Therefore, cost of 3 pounds of oranges = 3 × 0.6 = 1.8

use this formula:

p(a\b) = p(a and b)/p(b).

take it from here.

-2x + 7 = 7

subtract 7 from both sides.

-2x = 0

divide both sides by -2.

x = 0