Studying 30 minutes a day maybe longer
Answer:
the answer should be y=-1/4
$7.9 cost of one pack
10 packs cost is $79
She pays $29 + Voucher
From the total $79 we substract the $29 she paid with cash or card.
79-29=50
So the value of the voucher is $50
PS: celia should cut on chocolate. Not healthy for her :)
I believe the answer to this question is: the last one.
