Answer:

Step-by-step explanation:









<h3>Hope it is helpful....</h3>
x/20 = 21/14 (similar proportions)
x/20 = 3/2 (simplify by canceling out a factor of 7)
x = 30
10% of 80 = 8
80 - 8 = 72
if they are 10% off, the contact lenses will cost $72
Answer:
(7, 6)
Step-by-step explanation:
multiply first eq. by 3 to get 6x - 3y = 60
now do
6x + 3y = 60
- 6x - 5y = 12
--------------------
8y = 48
solve for y: y = 6
with this y value, plug it in to the first equation (easier to solve) and get 2x + 6 = 20
solve for x and get x = 7
so ans is (7, 6)
Twenty-five times two = fifty