What integer is the opposite of 12?

Can someone check my answer? you : )

Determine the number of girls in a math class with 87 boys if there are 25 girls for every 75 boys

The party planning committee has to determine the number of tables needed for an upcoming event. if a square table can fit 8 people and a round table can fit 6 people, the equation 150 = 8x + 6y represents the number of each type of table needed for 150 people.