Answer:
Step-by-step explanation:
Let the three numbers be represented by a, b, c. Apparently, we want ...
a + b = c + 20
a + c = b + 30
b + c = a + 40
Adding these three equations gives ...
2a +2b +2c = a + b + c + 90
Subtracting a+b+c, we have ...
a + b + c = 90
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Now, we can subtract each original equation from this to find one of the variables:
(a +b +c) -(a +b) = (90) -(c +20)
2c = 70
c = 35
(a +b +c) -(a +c) = (90) -(b +30)
2b = 60
b = 30
c = 90 -35 -30 = 25
The three numbers are 25, 30, 35.