Answer:
number of packs of chewing gum is 7
number of mints is 6
number of chocolate bars is 2
Step-by-step explanation:
number of packs of chewing gum → x, cost 6¢
number of mints → y = x-1 =3z, cost 3¢
number of chocolate bars → z = y/3 = (x-1)/3, cost 10¢
put in equation 6x + 3y +10z = 80 plug in term of x
6x +3(x-1) +10((x-1)/3) =80 multiply each side by 3
18x +9(x-1) +10(x-1) =240 distribute
18x+9x-9+10x-10 =240 combine like terms
37x-19 = 240 add 19 in each side
37x =259
x = 7
plug into y = x-1 = 7-1 = 6 so y=6
and z = y/3 =6/3 =2 so z = 2