On a recent test, Shawna was given the following problem:

A right triangle has side lengths 7 meters and a hypotenuse of 25 meters. The other side is labeled a.

Shawna's work is shown below:

1. a2+72=252

2. a2+14=50

3. a2=36

4. a=6 m

In which step did Shawna make an error?
Step 1. She incorrectly applied the Pythagorean theorem.
Step 2. She incorrectly squared the numbers.
Step 3. She incorrectly isolated a2
Step 4. She incorrectly solved for a.