Answer:
The first step to solve 2x-5=13 is "add by 5 from both sides".

Explanation:
To solve this problem, isolate it on one side of the equation.
Isolate the term of x.
2x-5=13
First, add by 5 from both sides.
⇒ 2x-5+5=13+5
Solve.
Add the numbers from left to right.
⇒ 13+5=18
→ 2x=18
Divide by 2 from both sides.
⇒ 2x/2=18/2
Solve.
Divide the numbers from left to right.
⇒ 18/2=9

The solution is x=9.
- Therefore, the correct answer is "add by 5 from both sides".