the sum of two numbers is 21 five times the first number added to 2 times the second number is 66 find the two numbers

Answer 1

a = first number

b = second number

The sum of two numbers is 21 mean:

a + b = 21

Five times the first number added to 2 times the second number is 66 mean:

5 a + 2 b = 66

a + b = 21 Subtract a to both sides

a + b - a = 21 - a

b = 21 - a

Replace this value in equation:

5 a + 2 b = 66

5 a + 2 ( 21 - a ) = 66

5 a + 2 * 21 - 2 a = 66

5 a + 42 - 2 a = 66

3 a + 42 = 66 Subtactt 42 to both sides

3 a + 42 - 42 = 66 - 42

3 a = 24 Divide both sides by 3

a = 24 / 3 = 8

b = 21 - a = 21 - 8 = 13

Answer 2

8 and 13