Answer:
The number in the middle is 60.
Step-by-step explanation:
The 2nd number = A
The 3rd number = B
The 4th number = C
Given:
(1) 130 + A + B = 300
(2) A + B + C = 200
(3) B + C + 10 = 100
Now, the work:
(2) can be modified to become A + B = 200 - C
Now, we can insert that into (1) and get the following;
130 + (200 - C) = 300
Open parentheses, simplify, you get C = 330 - 300.
C = 30
Using (3), we use above answer to get B + 30 + 10 = 100
Calculate, and get B = 100 - (30 + 10)
Simplify,
B = 60
There is your answer!
Cheers
