Answer:
3
Step-by-step explanation:
Choose a variable to represent the number to be added to 5 and 3.
[tex]\frac{5+x}{3+x}=\frac{4}{3}[/tex]
"Cross-multiply."
[tex]3(5+x)=4(3+x)\\\\15+3x=12+4x\\\\15=12+x\\\\3=x[/tex]
Check: The ratio of 5+3 to 3 + 3 is 8:6, equal to the ratio 4:3.