15 ! the sum of three numbers is 15 the second number is 2 times the first. the third number is 20 less than the second. what is the third number?

x+y+z=15

y =2x

z=y-20

substitute these equations into the first

x+2x+y-20 =15

now substitute 2x in for y

x + 2x +2x-20 =15

combine like terms

5x-20 =15

add 20 to each side

5x = 35

divide by 5

x=7

y =2x

y =14

z = y-20

z=14-20

z=-6

The third number is -6

answer: what

step-by-step explanation:

b if for most of the graph

d if y intercept

step-by-step explanation: