Using the elimination method to solve
2 x-y=8
x + y = 20

Step-by-step explanation:

2x-y=8

x+y=20

3x=28

×=28÷3=9.3

so

9.3+y=20

y=20-9.3

y=20.7

an altitude of 15,000 feet

step-by-step explanation:

c.

step-by-step explanation:

she should of added 9^2 and 12^2. that is because it is a^2+b^2=c^2. c^2 is the hypotenuse and should always be bigger than the other two numbers. which is why she should of added 9 squared and 12 squared together instead of 15 squared.