The right answer is Option A.
Step-by-step explanation:
Let,
x be the postcards
y be the large envelops
According to given statement;
14x+5y=12 Eqn 1
10x+15y=24.80 Eqn 2
Multiplying Eqn 1 by 3;

Subtracting Eqn 2 from Eqn 3;

Dividing both sides by 32

Putting x=0.35 in Eqn 1;

Dividing both sides by 5

Therefore, one large envelope costs $1.42
The right answer is Option A.
Keywords: linear equations, subtraction
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If you follow is rule : P(x,y)>180° rotation>P'(-x,-y). the negative signs doesn't mean to make it negative but to change it to the opposite sign. If it's positive it goes to negative. And if it's negative is goes to positive. The rotated image would have the points: (1,2) (4,4) (3,7)
13, because 442/34 is 13 meaning each person sold an equal amount