The sum of two number is 21 the larger number is 6 less than twice the smaller number. find the two numbers.

Okay so the answer is 5 & 16.

The work:
Let x = The smaller number

x + (2x + 6) = 21
\ / -6. -6
3x = 15

3x/3 = 15/3

x = 5

Since x is the smaller number, to find the other number you would need to multiply 5 by 2 and add 6 giving you 16 which is the other number. Hence 5+16=21.