Question 831621
Let A be the first aircraft
Let B be the second aircraft
Let C be the third aircraft
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Here is the information given in the question:
A = B + 81 (the first aircraft has 81 more seats than the second aircraft.)
C = B - 52 (The third aircraft has 52 fewer seats than the second aircraft.)
A + B + C = 425 (their total number of seats is 425)
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Now substitute the values in the 1st and 2nd equations into the 3rd.
(B+81) + B + (B-52) = 425
Add the Bs, and do the math
3B +29 = 425
Subtract 29 from each side
3B = 396
Divide each side by 3
B = 132
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Since we know B, we can find A (132+81=213), and C (132-52=80).
Let's prove it by adding the three together.
213 + 132 + 80 = 425
Success!