4. Rafael and Roger played tennis against each other 30 times.
Each of the times they played, either Rafael won or Roger won.
The ratio of the number of times Rafael won to the number of times Roger won is 7:3
(a) Work out the number of times Rafael won.
In a school, there are 75 girls in the tennis squad.
The ratio of the number of boys in the tennis squad to the number of girls in the tennis Squad is 4:3
(b) Work out the number of boys in the tennis squad.