When we multiply two negative numbers, one always gets a positive number.
(-)×(-)= +
Hope it helps
The angles form a right angle, so make an equation where they add up to 90 degrees.
(c + 3) + (4c - 13) = 90
Combine like terms.
5c - 10 = 90
Add 10 to both sides.
5c = 100
Divide both sides by 5.
c = 20
