need help with this word problem please!

Question

stuck on this on

 

Danielles chemistry teacher has a complicated grading system. each lab counts once and each test counts as two labs.at the end of the semester there is a final lab that counts as three regular labs. danielle received danielle received scores of 80, 84 and 87 on her labs, and scores of 83, and 89 on her tests. what score must she get on the final lab to receive an A in the class (an A is 85)?

Answer 1

Each lab counts once 80 + 84 + 87 = 251

 

Each test counts as two labs: 83 + 83 + 89 + 89 = 344

 

The final lab counts as 3 labs: x + x + x = 3x, where x is the unknown score on the final lab

 

We want the average to equal 85 (an A - wow, wish I'd gone to that school).  To get the average you must divide the sum of the scores by the number of scores, where the number of scores =10 (3 regular lab scores + 4 tests scores (2 tests counted double) + 3 final lab scores (final lab counted triple))

 

(251 + 344 + 3x)/10 =  85

 

595 + 3x = 850

 

Solve for x