Final answer:
Sadie finished her math test in 47 minutes.
Step-by-step explanation:
To find out how long it took Sadie to finish her math test, we need to set up an equation based on the given information. Let's say it took Laura x minutes to finish her test. According to the problem, Sadie finished her test in 16 minutes less than 3 times Laura's time, so Sadie finished in 3x - 16 minutes. The total combined time of both Sadie and Laura is 1 hour and 8 minutes, which is equal to 68 minutes. So, the equation becomes x + 3x - 16 = 68. To solve for x, we combine like terms and isolate x on one side of the equation. 4x - 16 = 68. Adding 16 to both sides, we get 4x = 84. Finally, dividing by 4, we find that x = 21. Therefore, it took Laura 21 minutes to finish her test. To find how long it took Sadie, we substitute x with 21 in the equation 3x - 16, which gives us 3(21) - 16 = 63 - 16 = 47. So, it took Sadie 47 minutes to finish her test.