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
