How to write 4 divisors of 240 that are multiple of tens

Asilkworm winds its cocoon out of one long silk fiber. to make silk thread, 3 to 10 of these silk fibers are unwound from their cocoons and combined into aa single thread with a typical length of 300 yards. choose a reasonable number of silk fibers in a thread write an equation to find the total length of the silk fibersused in 300 yards of the thread

This is about circle theorems. someone asap : (

Given: circle o, cd is diameter, chord ab || cd. arc ab = 74°, find arc ca.