Two numbers have a sum of 11 and a difference of 10.

X=10.5, Y = .5

Step-by-step explanation:

You set up 2 equations and then solve simultaneously.

X + Y = 11

X - Y  = 10

Add these 2 equations together and you get:

     2X  = 21

So,   X = 10.5 and therefore Y must = .5

the answer is 21%.

y=-2.5x+12.5

step-by-step explanation:

5y=2x+10

y=0.4x+2

slope=-2.5

5=-2.5*3+b

b=12.5