If you solve this algebraically there are 3 unknowns introduced in the problem and statements.
x = number of suits in 1990
y = number of suits in 1995
z = number of suits in 2000

From the question we know y = 2x. The question asks to find the value of x.

With statement 1, we know z = 2y. Typically with systems of equations we need as many equations as there are variables. By recognizing this on the data sufficiency you don't need to waste valuable time actually solving to find the value. Just determine you have enough information. At this point we have 3 variables and 2 equations so not enough information. So statement 1 is not sufficient, so eliminate A and D.

With statement 2, we know z = 2 + y. Again just 2 equations and 3 variables, so eliminate B.

When we combine the information we have 3 variables with 3 equations. We have as many different equations as variable, so both statements are sufficient and the answer is C.

Take care,
Sionainn