set up a table as follows:
x y
CRT LCD total
material 60 120 = 9720
labor 90 130 = 11580
x is equal to the number of CRT.
y is equal to the number of LCD
total material is equal to 9720.
total labor is equal to 11580.
you have two equations that need to be solved simultaneously.
they are:
60x + 120y = 9720
90x + 130y = 11580
we'll solve by elimination.
multiply both sides of the first equation by 1.5 and leave the second equation as is to get:
90x + 180y = 14580
90x + 130y = 11580
subtract the second equation from the first equation to get:
50y = 3000
solve for y to get y = 60
replace y in the first original equation with 60 and solve for x to get:
60x + 120y = 9720 becomes 60x + 7200 = 9720.
solve for x to get x = 42.
your solution is x = 42 and y = 60
this means that you will manufacture 42 CRT and 60 LCD.
your original equations of:
60x + 120y = 9720
90x + 130y = 11580
become:
60 * 42 + 120 * 60 = 9720
90 * 42 + 130 * 60 = 11580
simplify to get:
9720 = 9720
11580 = 11580
x represents the number of CRT which is equal to 42.
y represents the number of LCD which is equal to 60.
solution looks good.