Mr. Li did 150 push – ups on Monday.
Solution:
Given, Mr. Li did some push-ups on Monday and Tuesday.
On Tuesday, he did 300 push-ups,
Which was three times the difference of the number of push-ups he did on Monday and the number 50.
We have to find how many push - ups did he do on Monday?
Let the number of push – ups on Monday be n
Now, three times the difference of n and 50 = 300
3 x (n – 50) = 300
n – 50 = 100
n = 150
Hence, he did 150 push – ups on Monday.