The answer is A because the sign changes
Let's call:
f = price of 1 cup of dried fruit
a = price of 1 cup of almonds
In order to build the linear system, you need to consider that the total price of a bag is given by the sum of the price of cups times the number of cups in each bag, therefore:

Solve for a in first equation:
a = (6 - 3f) / 4
Then substitute in the second equation:
41/2 f + 6 · (6 - 3f) / <span>4 = 9
41/2 f + 9 - 9/2 f = 9
16 f = 0
f = 0
Now, substitute this value in the formula found for a:
</span>a = (6 - 3·0) / <span>4
= 3/2 = 1.5
Hence, the cups of dried fruit are free and 1 cup of almond costs 1.5$</span>
A^2 + b^2 = c^2
a^2 + 12^2 = 13^2
a^2 + 144 = 169
a^2 = 25
a = 5
Answer: The number he needs, a, is 5
Well if she skips 4 times per second and there are 60 seconds in a minute you will multiply 4 by 60 and you should get the answer 240