Answer:
48
Step-by-step explanation:
Ratio: Blue:yellow=4:3
[tex]4:3=7\\?:?=84\\84/7=12\\[/tex]
4x12=48
So basically, You make a "equation".
You add 4 and 3 which is 7.
So since you know there is 84 total cards. That will equal the "?". So you divide the 84 and 7 since that will show what you will multiply with 4 and 3 to keep the blue and cards equally balanced. So you multiply the 12 and 4. Which is 48.
So there are 48 blue cards. Hope this helped you C: