Question 980590


Let &nbsp;<B>x</B>&nbsp; be the mass of the first alloy &nbsp;(first piece)&nbsp; in kilograms, &nbsp;and let &nbsp;<B>y</B>&nbsp; be the mass of the second alloy &nbsp;(second piece)&nbsp; in kilograms.


Then you have first equation 


x + y = 20.


The first alloy contains &nbsp;0.3*x&nbsp; kilograms of nickel, &nbsp;and the second alloy contains &nbsp;0.7*y&nbsp; kilograms of nickel. &nbsp;Therefore the mix contains &nbsp;0.3*x + 0.7*y&nbsp; kilograms of nickel. 


It gives you the second equation


0.3*x + 0.7*y = 0.48*20 = 9.6.


So, &nbsp;you have the system of two linear equations in two unknowns


{{{system(x + y = 20,
0.3*x + 0.7*y = 9.6)}}}.


Solve yourself this system.