Nina is 10 years younger than Deepak. Deepak is 3 times as old as Nina. Which system of equations can be used to find d, Deepak's age, and n, Nina's age?
d = n + 10
d = 3n
d = n − 10
d = 3n
d = n + 10
n = 3d
d = n − 10
n = 3d