Jenny's mean score on three science tests was 75. Her last two scores were 79 and 80. She forgot her score on the first test. What was it?

57 (3 * 75) - 79 - 80 = ?

To find Jenny's score on the first test, we need to calculate the sum of the three scores and then subtract the sum of her last two scores from it.

Let's break it down step by step:

Step 1: Add the last two scores (79 and 80)
79 + 80 = 159

Step 2: Subtract the sum of the last two scores from the mean score (75)
75 - 159 = -84

Therefore, Jenny's score on the first test was -84.

However, this result seems unlikely because test scores are typically positive values. It's possible that there is an error or missing information in the given problem.