One year there was a total of 84 commercial and noncommercial launches. The number of noncommercial orbital launches was 4 more than 3 times the number of commercial orbital launches. Determine the number of commercial and noncommercial launches.

Question

anonymous · Answer

Let c=commercial and n=noncommercial.
n=3c+4
c+n=84
Already have n solved, so substitute that value is second equation.
c+(3c+4)=84
4c+4=84
4c=80
c=20
Solve for n using second equation.
20+n=84
n=64

There was 20 commercial launches and 64 noncommercial launches

anonymous · Answer

x = commercial, non commercial launches = 3x + 4
so 
x + 3x + 4 = 84
4x = 80
x = 20

so 20 commercial launches and 84-20 = 64 non commercial launches