Solve the system by substitution.
y = -X
y = - 4x + 12

International calls require the use of a country code. many country codes a 3-digit numbers. country codes do not begin with a 0 or 1. there are no restrictions on the second and third digits. how many different 3-digit country codes are possible?

If 25% of y is 30, what is 60% of y?

Which number line correctly shows 0.8 + 0.3?