Answer = 9/10
Step-by-step explanation:
Add up all the frequencies along the bottom row: 15+20+40+15+10 = 100
There are 100 pitches total. Ten of which occurs when the pitcher throws 5 times at the batter, as shown in the far right-most column. This means 100-10 = 90 occurrences happen when the pitcher throws 4 or fewer pitches to the batter.
The probability your teacher wants is therefore 90/100 = 9/10. This answer is in fraction form. It is equivalent to the decimal form 0.9