One number is 2 times another number plus 3. Their sum is 21. Find the numbers.

If x represents the smaller number, which of the following equations could be used to solve the problem?

2x + 3 = 21
3x + 3 = 21
3x + 6 = 21

Question

One number is 2 times another number plus 3. Their sum is 21. Find the numbers.

If x represents the smaller number, which of the following equations could be used to solve the problem?

2x + 3 = 21
3x + 3 = 21
3x + 6 = 21

anonymous · Answer

Let first number be x and the second number be y
y = 2x + 3_______1
x + y = 21
y = 21 - x _______2
Substitute 2 into 1
21 - x = 2x + 3
Rearrange the equation ^
2x + 3 = 21 - x
3x + 3 = 21
THEREFORE, The 2nd option out of the three is correct.