What is the highest common factor of 20 and 30

10

Step-by-step explanation:

the factors of 20 are 1, 2, 4, 5, 10, 20

the factors of 30 are 1, 2, 3, 5, 6, 10, 15, 30

the common factors are 1, 2, 5, 10

the highest common factor is 10

Sophia wrote the number 41.

Step-by-step explanation:

Let x by the two-digit number written by Sophie. Max appended a 3, so the new number is 10x+3.

The difference between Max's and Sophie's numbers is 372:

(10x+3)-x=372

9x+3=372

9x=369

x=41.

So, Sophie's number was 41.