List two pairs of angles in square CDFG that are complementary

How do you find the area of this triangle.

Carter drank 15.75 gallons of water in 4 weeks. he drank the same amount of water each day.a. estimate how many gallons he drank in one day.b. estimate how many gallons he drank in one week.c. about how many days altogether will it take him to drink 20 gallons?

The angle of a triangle are given as 6x,(x-3), and (3x+7). find x then find the measures of the angles