Question 1110861
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I can easily write the problem as a system of 3 equations in 3 unknown, but I think it would be bad help to you.


Much better is to reduce it to the system of 2 equations in 2 unknowns.


Let M be the number of classes in Math and C be the number of classes in Calculus.


Then the number of classes in CompSci is (7-M-C).


Now your system of equations is

40M + 40C + 10*(7-M-C) = 220     (1)    (counting students)
40M + 60C + 27*(7-M-C) = 294     (2)    (counting thousands of dollars)


At this point, the setup is completed, as well as my role as a tutor.


Next you should to simplify the system; to write it in the standard form and to solve it.
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To see many other similar solved problems, &nbsp;look into the lessons

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/coordinate/lessons/How-to-algebreze-and-to-solve-this-problem-on-2-eqns-in-2-unknwns.lesson>HOW TO algebreze and solve this problem on 2 equations in 2 unknowns</A> 

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/coordinate/lessons/One-unusual-problem-to-solve-using-system-of-two-equations.lesson>One unusual problem to solve using system of two equations</A> 

in this site.


Also, &nbsp;you have this free of charge online textbook in ALGEBRA-I in this site

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson>ALGEBRA-I - YOUR ONLINE TEXTBOOK</A>.


The referred lessons are the part of this online textbook under the topic "<U>Systems of two linear equations in two unknowns</U>".



Save the link to this online textbook together with its description


Free of charge online textbook in ALGEBRA-I
https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson


to your archive and use it when it is needed.