Two cars leave Peoria at the same time, one heading east at 60 mph and the other west at 70 mph. How long (in hr) will it take them to be 845 miles apart?

The cost per student for a field trip to the Everglades varies inversely as the number of students who attend. It will cost each student $250 if 24 students attend. How many students would have to attend to get the cost down to $200?

Gold is alloyed with different metals to make it hard enough to be used in jewelry. The amount of gold present in a gold ally is measured in 24ths called karats. 24-karat gold is 100% gold. Similarly, 12-karat gold is 50% gold. 
How many ounces of 4-karat gold should be added to 8 ounces of 8-karat gold to make an amount of 6-karat gold? Graph equations on coordinate axes with labels and scales. *

the equation a= 6d-4 represents the relationship between the age of a tree in years, a, and its diameter in centimetres, d, what is the diameter of a tree that's 75 years old