740,000,000 left handed people
6,660,000,000 right handed people 
Steps: 
10% is equal to 0.1 
7,400,000,000 multiplied by 0.1 
Equals 740,000,000 left handed 
Total amount of people subtract left handed people equal right handed people 
7,400,000,000 - 740,000,000 = 6,660,000,000 right handed people