Explanation:
You could use a calculator to make it simple
(0.067 × 42.1) ÷ (17.4 - 4.19). to 1s.f
=(2.8207) ÷ (13.21)
= 0.213527 to 1s.f
= 0.2
*you could also check using your own calculator
*let me know if you want me to expand it if you don't have a calculator