Question:
One number is 7 times a first number. A third number is 100 more than the first number. If the sum of the three numbers is 505, Find the numbers.
Answer:
The numbers are 45, 315 and 145
Explanation:
Represent the three numbers with A, B and C
Required
Find A, B and C
From the first statement;

--- (i)
From the second;
---- (ii)
From the third;
---- (iii)
Substitute 7A for B and 100 + A for C in (iii)

Collect like terms


Divide both sides by 9

Substitute 45 for A in (i)



Substitute 45 for A in (ii)



Hence, the numbers are 45, 315 and 145