Let's solve the given equation step by step:
The equation representing the situation is:
[tex]\[ 2n + 1 = 157 \][/tex]
### Step 1: Isolate [tex]\( n \)[/tex]
First, subtract 1 from both sides of the equation to isolate the term involving [tex]\( n \)[/tex]:
[tex]\[ 2n + 1 - 1 = 157 - 1 \][/tex]
[tex]\[ 2n = 156 \][/tex]
### Step 2: Solve for [tex]\( n \)[/tex]
Next, divide both sides of the equation by 2 to solve for [tex]\( n \)[/tex]:
[tex]\[ \frac{2n}{2} = \frac{156}{2} \][/tex]
[tex]\[ n = 78 \][/tex]
So, the first number is [tex]\( 78 \)[/tex].
### Conclusion
The correct answer is:
[tex]\[ \text{B. } 78 \][/tex]
