Two decimal numbers have a difference of 0.7 and and a sum of 1.what are the numbers?

The two numbers are 0.85 and 0.15
if you add them together you get 1, 0.85+0.15=1
and if you subtract them you get 0.7, 0.85-0.15=0.7

Use an equation for questions like these:
I'll use x and y as the unknown numbers
x-y=0.7
x+y=1
Just choose either x or y to solve for
y=x-0.7
y=-x+1
Then since since they're both equal to y then they can equal each other
x-0.7=-x+1
2x-0.7=1
2x=1.7
x=0.85
Then just grab one of the equations and use it to find y
0.85+y=1
y=0.15

So the two numbers are 0.85 and 0.15