Question 616075
Let us say that the total number of regular admission tickets is a and the total number of senior tickets is s.

So each sale of one of these tickets brings in $4 and $3 respectively

So:

(a x 4) + (s x 3) is the total sales which is $720

i.e. 

4a + 3s = 720

We also know the total number of people was 190 so:

a + s = 190

So if we rearrange the second equation we can get:

s = 190 - a

Now we substitute this into the first equation:

4a + 3(190 - a) = 720

4a + (570 - 3a) = 720

4a + 570 - 3a = 720

4a - 3a = 720 - 570

a = 150

so 150 regular admission tickets were sold !!!