The answer is (C) because both pieces of information are required to determine last year's revenue:

Revenue - Expenses = Gross Profit

(1) Provides us with this piece of the equation:
Revenue - Expenses = 4100

(2) Provides us with this information:
Revenue = 1.5 x Expenses

Together, the two pieces of information provide for the following substitution:
Revenue - Expenses = 4100
(1.5 x Expenses) - Expenses = 4100
.5 x Expenses = 4100
Expenses = 8200
Revenue - 8200 = 4100
Revenue = 12,300

stevestein wrote:The answer is (C) because both pieces of information are required to determine last year's revenue:

Revenue - Expenses = Gross Profit

(1) Provides us with this piece of the equation:
Revenue - Expenses = 4100

(2) Provides us with this information:
Revenue = 1.5 x Expenses

Let's stop right here and use my favourite DS tool: number of equations vs number of unknowns.

Here's the MOST important rule to know and love for DS:

To solve a system of n variables, one requires n distinct linear equations.

Learn that rule. Hug that rule. Love that rule so much that you marry it!

Q Stem: 1 equation, 3 variables.

(1) 1 more equation, doesn't eliminate the 2 variables we don't want: insufficient.

(2) 1 more equation, doesn't eliminate the 2 variables we don't want: insufficient.

Together: 3 variables, 3 distinct linear equations. We have enough information to answer ANY question about the system: sufficient, choose (C).

Note that no math was harmed in the solving of this question!