1. 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. how many push-
ups did he do on monday?

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.

you can't solve x because it is 2 linear equation and you only have one equation