SOLUTION: Karim took 7 hours to drive 680km. The first part of the trip, he drove at 80km/h. He then increased his speed by 30km/h for the remainder of the trip. How far did he drive at each

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Question 184244: Karim took 7 hours to drive 680km. The first part of the trip, he drove at 80km/h. He then increased his speed by 30km/h for the remainder of the trip. How far did he drive at each speed?
Answer by PoCTo(1) About Me  (Show Source):
You can put this solution on YOUR website!
Let t1 be the time with 80km/h, and t2 - with 80+30=110km/h. So we have a linear system:
Solved by pluggable solver: SOLVE linear system by SUBSTITUTION
Solve:
+system%28+%0D%0A++++80%5Ct1+%2B+110%5Ct2+=+680%2C%0D%0A++++1%5Ct1+%2B+1%5Ct2+=+7+%29%0D%0A++We'll use substitution. After moving 110*t2 to the right, we get:
80%2At1+=+680+-+110%2At2, or t1+=+680%2F80+-+110%2At2%2F80. Substitute that
into another equation:
1%2A%28680%2F80+-+110%2At2%2F80%29+%2B+1%5Ct2+=+7 and simplify: Error: 'Can't call method "invoke_solver" on an undefined value at /home/ichudov/project_locations/algebra.com/templates/Algebra/Solver/PerlSolver.pm line 115. Can't call method "invoke_solver" on an undefined value at /home/ichudov/project_locations/algebra.com/templates/Algebra/Solver/PerlSolver.pm line 115. '. Can't call method "invoke_solver" on an undefined value at /home/ichudov/project_locations/algebra.com/templates/Algebra/Solver/PerlSolver.pm line 115. Can't call method "invoke_solver" on an undefined value at /home/ichudov/project_locations/algebra.com/templates/Algebra/Solver/PerlSolver.pm line 115.
error_location: 101