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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Answer:
The legs of a 45 45 90 triangle are congruent so if one leg is x we can write (using the Pythagorean Theorem):
x² + x² = 18²
2x² = 324
x² = 162
x = 9√2
Answer:
6.8 gallions i believe. im not quite sure