Answer:
1 cupcake = $3.75
1 ice-cream = $4.50
1 doughnut = $1.50
Step-by-step explanation:
2 ice-cream + 1 cup cake = $12.75 ------------ [ 1 ]
1 ice-cream + 2 doughnuts = $7.50 ------------ [ 2 ]
1 cup cake + 1 doughnut + 1 ice-cream = $9.75 ------------ [ 3 ]
From [ 1 ] :
2 ice-cream + 1 cup cake = $12.75
1 cupcake = $12.75 - 2 ice-cream
Substitute [ 1 ] into [ 3 ]:
1 cup cake + 1 doughnut + 1 ice-cream = $9.75
$12.75 - 2 ice-cream + 1 doughnut + 1 ice-cream = $9.75
1 doughnut - 1 ice-cream = -$3 ------------ [ 4 ]
[ 2 ] + [ 4 ] :
3 doughnuts = $4.75
1 doughnut = $1.50
Substitute (1 doughnut = $1.50) into [ 2] :
1 ice-cream + 2 doughnuts = $7.50
1 ice-cream + 2 x $1.50 = $7.50
1 ice-cream + $3 = $7.50
1 ice-cream = $4.50
Substitute (1 ice-cream = $4.50) into [ 1 ]:
2 ice-cream + 1 cup cake = $12.75
2 x $4.50 + 1 cup cake = $12.75
1 cupcake = $12.75 - $9
1 cupcake = $3.75
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