How do I answer A and B?

Answer:
Step-by-step explanation:
a) We're working with the ratio 3:1
x:500
500/1 = 500
500 * 3 = 1,500
x = 1,500
She would need to use 1,500 mL of yellow ink.
b) We're working with the ratio 2:3
x:750
750/3 = 250
250 * 2 = 500
x = 500
She would need to use 500 mL of red ink.
You can check both of these by:
(a) 1,500/500 = 3/1 = 3 : 1 which is the ratio we're working with.
(b) 500/2 = 250
750/2 = 375
250 : 375
Then, divide both 250 and 375 by 125
250/125 = 2
375/125 = 3
We are then left with the ratio 2 : 3 which is the ratio we're working with.