To factor the expression you need to find the greatest common factor of the terms. The greatest common factor (GCF) is the highest number that will be into both terms. Since there's nothing that will fit into both x and y, you'll only need to find the GCF of the coefficients.
16x + 40y To start, list the factors of both numbers
16: 1, 2, 4, 8, 16
40, 1, 2, 4, 5, 8, 10, 20, 40
You can see that 8 is the highest number that will go into 16 and 40. So, you can pull the 8 out of the expression.
8(2x + 5y)