What’s the GCF of 84 and 42

need help my boyfriend needs da help! and it needs too be worked out like the pic says

the 2 figures are congruent bc if you reflect abcd over the y axis then over the d axis the figures overlap

on monday rodney ate 1/4th of the sandwich = 3/12

on tuesday he ate 1/3rd of the sandwich = 4/12

therefore in total he has eaten = 3/12 + 4/12 = 7/12

thus we can say that he has eaten 7/12 of the sandwich on monday and tuesday alltogether.

happy to

pls mark as brainliest.