let's firstly convert the mixed fraction to improper fraction and then take it from there, keeping in mind that the whole is "x".
So, put 2 hours into minutes. You get 120. Now, seeing how you have 20 song requests, and each one takes 3.5 minutes, multiply those two values. Now you have 70. After doing that, just subtract 70 from 120 and get 50.
tada
answer is 50
I believe it is 8,000 grams :).
Its a simultaneous equation:
lets make "x" the used games and "y" the new ones
4x + 2y = 84
6x + y = 78. (multiply this by 2 to cancel out y)
12x + 2y = 156
so now we subtract them:
12x - 4x = 156 - 84
x = 9
used games cost $9
new games cost 78 - 6(9) = $24
Janet has $120 but she already bought 3 NEW games so:
120 - 3(24) = $48 left
48/9 = how many used ones she can buy = 5. something
she can buy 5 used