80% of 20 is 80/100 x 20 = 16
So, kelly has used 16 stamps, and has 4 left
Answer:
x = 4
Step-by-step explanation:
DE is parallel to AC and intersects the other 2 sides. It divides those sides proportionally, that is
=
, thus
=
( cross- multiply )
2(10 - x) = 3x ← distribute left side
20 - 2x = 3x ( subtract 3x from both sides )
20 - 5x = 0 ( subtract 20 from both sides )
- 5x = - 20 ( divide both sides by - 5 )
x = 4
2+4=4+2 is an example of commutative property of addition