AlgebraEasy–MediumReading one variable from a two-variable equation in context
Algebra practice question
A florist sells roses for $2 each and lilies for $5 each. The equation 2r + 5l = 20 relates the numbers of roses r and lilies l in a $20 bunch. If the bunch has 2 lilies, how many roses does it have?
Answer: 5
Substitute l = 2: 2r + 10 = 20, so 2r = 10 and r = 5.
Common wrong answers
- If you answered 10
- 10 is 2r, the money spent on roses, not the number.
- If you answered 15
- 15 comes from 20 − 5, subtracting one lily's price instead of two.
- If you answered 2.5
- 2.5 divides 5 by 2 in error; 2r = 10 gives r = 5.
More Algebra questions
- Easy–Medium
A line passes through the points (0, 3) and (2, 7). What is the slope of the line? - Easy–Medium
A gym charges a $25 one-time signup fee plus $15 per month. Which equation gives the total cost C, in dollars,… - Easy–Medium
If 5(x − 2) = 3x + 4, what is the value of x? - Easy–Medium
A taxi charges a $3.50 base fare plus $2.25 per mile. If a ride costs $19.25 total, how many miles was the rid… - Easy–Medium
The equation of a line is 3x + 2y = 12. What is the y-coordinate of the point where the line crosses the y-axi… - Easy–Medium
A line in the xy-plane passes through the points (1, 5) and (4, 11). What is the y-intercept of the line?
Not affiliated with the College Board. SAT is a trademark of the College Board.