The sum of two numbers

Question

The sum of two numbers is 158. If four times the smaller number is subtracted from the larger number, the result is 13. Find the two numbers. Larger and smaller

Answer 1

1. A + B = 158
2. A - 4B = 13

It is a system of equations with 2 variables. Using elimination if we subtract Eqn2 from Eqn1 we are left with

5B = 145

B = 29

A + 29 = 158

A = 129

Answer 2

You have 2 unknowns, therefor you need 2 equations.

Call the unknowns X and Y.

From the 1st sentence:

EQN-1: X + Y = 158

From the 2nd sentence:

EQN-2: Y - 4X = 13

subtract EQN-2 from EQN-1:

5X = 145

So X = 29

Use either EQN-1 or -2 to find Y