Question 1142577
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Let x = the amount invested at 10% and y = the amount invested at 18%.


Then from the condition you have these two equations in two unknowns


        x +     y = 138600  dollars    (1)    (total investment)

    0.10x + 0.18y =  18740  dollars    (2)    (total interest)


Solve the system by the Substitution method.

For it, from equation (1) express x = 138000 - y  and substitute it into equation (2). You will get


    0.10*(138600-y) + 0.18y = 18740


Simplify and express y from the last equation; then calculate


    y = {{{(18740 - 0.1*138600)/(0.18 - 0.10)}}} = 61000.


To find x, substitute the found value of y into equation (1). You will get then


    x = 138600 - 61000 = 77600.


<U>ANSWER</U>.  $77600 was invested at 10%  and  $61000 was invested at 18%.


<U>CHECK</U>.   0.10*77600 + 0.18*61000 = 18740  dollars.    ! Correct !
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Solved.


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It is a typical and standard problem on investment.


To see many other similar solved problems on investment, &nbsp;look into the lesson

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/coordinate/lessons/Using-systems-of-equations-to-solve-problems-on-investment.lesson>Using systems of equations to solve problems on investment</A>

in this site.


You will find there different approaches &nbsp;(using one equation or a system of two equations in two unknowns), &nbsp;as well as 
different methods of solution to the equations &nbsp;(Substitution, &nbsp;Elimination).


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 lesson is the part of this online textbook under the topic &nbsp;"<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.