Question

Of the three numbers, the sum of the first two is 45; the sum of the second and the third is 55 and the sum of the third and thrice the first is 90. The third number is:

Answer 1

Let the first number = x, the second number = y, and the third number = z

x + y = 45 ... (1)
y + z = 55 ... (2)
z + 3x = 90 ... (3)

Eliminate y using (1) & (2) equation
x + y = 45
y + z = 55 -
------------------
x - z = -10 ... (4)

Eliminate z using (3) & (4) equation
z + 3x = 90
x -   z  = -10 +
--------------------
4x = 80
x = 80 : 4
x = 20

z + 3x = 90
z + 3 × 20 = 90
z + 60 = 90
z = 90 - 60
z = 30

x + y = 45
20 + y = 45
y = 45 - 20
y = 25

The first number is 20
The second number is 25
The third number is 30

Answer 2

Answer:

I hope this helps! :)

Step-by-step explanation: