Answer:
(a) 25%
(b) 3:1
Explanation:
A shade of orange paint is made with 5 parts red paint and 15 parts yellow paint.
(a)
Total parts used in making orange paint=(5+15)+20 parts.
Number of parts of red paint used=5
Percent of paint is red=

=

=25%
Hence 25% of red paint was used to make orange paint.
(b)
The simplified ratio of yellow to red paint is:

Hence, the ratio is: 3:1.