Alright, let's solve the given problem step-by-step.
We are given the equation:
[tex]\[ 2n + 1 = 157 \][/tex]
where [tex]\( n \)[/tex] is the first number.
Step 1: Subtract 1 from both sides of the equation to isolate the term with [tex]\( n \)[/tex]:
[tex]\[ 2n + 1 - 1 = 157 - 1 \][/tex]
[tex]\[ 2n = 156 \][/tex]
Step 2: Divide both sides 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].
The correct answer is:
B. 78
