Two numbers have a difference of 0.85 and a sum of 1 what are the numbers?

let the two numbers be: x & y

x - y = 0.85

x + y = 1

Isolate the x. Subtract y from both sides

x + y (-y) = 1 (-y)

x = 1 - y

Plug in 1 - y for x in the other equation

x - y = 0.85

(1 - y) - y = 0.85

Simplify

1 - 2y = 0.85

Isolate the y. Note the equal sign. What you do to one side, you do to the other. Do the opposite of PEMDAS.

1 (-1) - 2y = 0.85 (-1)

-2y = -0.15

-2y/-2 = -0.15/-2

y = -0.15/-2

y = 0.075

Plug in 0.075 into one of the equations

x = 1 - y

x = 1 - (0.075)

x = 0.925

hope this helps