Question 122914
First you figure out how much it is going to cost for the rocks.  Since one ton of rock costs $60 and you need 30 tons, you multiply 60 by 30 and that equals 900, which is $900.  Then, you subtract the $900 dollars from the budget of $2500.  That equals $1600.  Now you can buy the trees.  The trees cost $84 each.  You divide 1600 by 84 and you get approximately 19 trees.  So the answer to the question of what is the minimum number of trees you can buy with your budget is 19 trees.
Hope this works out!!