The running time for movie A is 33 mins more than twice the running time for movie B. If the running time for movie A is subtracted from triple the running time for movie B, the result is 57 mins. find the running time for each movie..
Movie A-
Movie B-
for this to work we need to substitute a variable to get rid of it. look at 57=3b-a (lets switch it around s that the equation reads "a=") 57+a=3b a=3b-57 (this is our new equations)
so now we know that a=33+2b & a=3b-57 so we can write 33+2b=3b-57. we have now "gotten rid" of "a"
SOLVE FOR B
33+2b=3b-57 (get variable alone) 33= 3b-2b-57 (subtract and add accordingly) 33= b-57 33+57=b 90=b (this means that movie b is 90 long)
SOLVE FOR A
you can plug "b" into any of the original equations.
a=33+2b a=33+2(90) a=33+180 a=213
CHECK
plug "a" into any of the original equations to find "b" if b=90 then you know you've done it right
