Question

Using substitution, which number from the set {6, 13, 18, 26} makes the equation 2x+5=31 true?
Responses

18
26
6
13

Answer 1

First we substitute 18 into the equation:

2(18) + 5 = 31
36 + 5 = 31
41 = 31

This is not true, so we eliminate 18 from the set.

Next, we substitute 26 into the equation:

2(26) + 5 = 31
52 + 5 = 31
57 = 31

This is also not true, so we eliminate 26 from the set.

Then we substitute 6 into the equation:

2(6) + 5 = 31
12 + 5 = 31
17 = 31

This is also not true, so we eliminate 6 from the set.

Finally, we substitute 13 into the equation:

2(13) + 5 = 31
26 + 5 = 31
31 = 31

This is true, so the answer is 13.