Answer:
311 students prefer sushi
Step-by-step explanation:
Let
x------> the number of students who prefer pizza
y -----> the number of students who prefer sushi
we know that
-----> equation A
-----> equation B
Substitute the equation B in equation A and solve for y

600 *2*x + 150*4*x = 90
1200x + 600x = 90
1800x = 90
x = 90/1800 = 0.05
x = 5%
Answer: rate of interest = 5%
The answer would be d , because you have to add how many of each fish to equal up to the sum of 420 . which is x y . so the first equation is x + y = 420 . then it says he bought 6 times as many parrotfish as he did angelfish so you would have to multiply x which represents angelfish by 6 . to get the second equation of y = 6x .
To find the volume of the prism you are going to use the formula V=WxLxH.
When you plug in your numbers you should get V= 18x6x9 which ends up equaling 972.
Now that you have that you need to find the volume of the pyramid using the formula V= L x W x H /3 and when you plug that in it looks like
V= 18 x 6 x 15 /3
Upon simplifying that you get 540.
Now you have the volume of your rectangular prism and your rectangular pyramid add them together and you should get 1512
I recommend drawing it out... it helps a lot:)