Question 247998
jockey must play 14 commercial spots during 1 hour of a radio show,
 each commercial is either 30 seconds or 60 seconds long,
 if the total commercial time during 1 hour is 11 minutes, how many 30 second commercials were played that hour? 
and how many 60 second commercials were played that hour? 
:
Let x = no. of 30 sec spots
Let y = no. of 60 sec spots
:
Let's do everything in minutes; 60 sec = 1 min; 30 sec = .5 min
:
Write an equation for the number of commercials (14)
x + y = 14
:
Write an equation for the total time of the commercials (11 min)
.5x + y = 11
:
Subtract this equation from the 1st equation
x + y = 14
.5x + y = 11
---------------subtraction eliminates y, find x
.5x + 0 = 3
x = 2(3)
x = 6 ea 30 sec commercials
:
Find the no. of 60 sec commercials
14 - 6 = 8 
;
:
Check n the total time equation
.5(6) + 1(8) = 
3 + 8 = 11 minutes