How do you subtract a negative 9 from a positive 8

The line y = x + passes through (−3, 7) and is parallel to y = 4x − 1.

The clayton family’s pool has vertices at the coordinates (0, 2), (0, 5), (2, 5), (2, 6), (5, 6), (5, 1), (2, 1), and (2, 2). if each grid square has an area of 9 square feet, what is the area of the pool?

The ratio of the measures of the three angles in a triangle is 2: 9: 4. find the measures of the angels