Answer:
-5
Step-by-step explanation:
Steps to solve:
3(5x - 8) = 6x + 39
~Distribute left side
15x - 24 = 6x + 39
~Add 24 to both sides
15x = 6x + 63
~Subtract 6x to both sides
9x = 63
~Divide 9 to both sides
x = 7
Best of Luck!
Answer:
c 510
Step-by-step explanation:
hope this helps
Try this way:
1. note, that in such tasks mass of <u>pure</u> copper before merging and after merging is the same (this is the base);
2. If the mass of pure copper in alloy with 40% solution is 'x' and the mass of pure copper in alloy with 80% solution is 'y', then It means before merging was x/0.4 and y/0.8, after merging was (x+y)/0.7. It is one equation of the future system.
3. Using 120 kg. of 70% solution, it is possible to define mass of pure copper after merging, 120*0.7(=84 kg.). And before merging it was 'x+y' kg. of pure copper. It is the second equation of the future system.
4. according to the items no.2&3 (to make up the system of two equations and solve it). All the details are in the attached picture.
5. pure copper in 40% solution is 12 kg., pure copper in 80% solution is 72 kg. It means, that the copper alloy with 40% solution is x:0.4=12/0.4=30 kg., and the copper alloy with 80% solution is y:0.8=72/0.8=90 kg.
14.5 is the answer to the equation