Source: Official Guide for the GMAT 12th Ed. Section 6.3 Data Sufficiency; #137

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# At a bakery, all donuts are priced equally

At a bakery, all donuts are priced equally and all bagels are priced equally. What is the total price of 5 donuts and 3 bagels at the bakery? (1) At the bakery, the total price of 10 donuts and 6 bagels is \$12.90. (2) At the bakery, the price of a donut is \$0.15 less than the price of a bagel. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient., Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient., BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient., EACH statement ALONE is sufficient., Statements (1) and (2) TOGETHER are not sufficient.

### 2 Explanations

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Sam Nepomuceno

Hi!

Why can't i substitute D=B - 0.15 into the prompt equation 5D + 3B = ?
Thank you!

Jul 2, 2016 • Comment

Sam Kinsman, Magoosh Tutor

Good question! If we have the two equations D = B - 0.15 and 5D + 3B = ?, we don't have enough information to find the value of any of the variables.

When we have two equations and two unknowns, that's enough information to find the value of both unknowns. However, here we have three unknowns: D, B and ? (the result of 5D + 3B). So we don't have enough information to solve this. Mike McGarry, Magoosh Tutor