Intro to Numerical Computation by FreeMat

In this lab we got introduced to a powerful freeware called MatLab. This program is used for calculations specially matrices. Matlab makes solvig the long equations with too many variables and equations easy.
To learn the basics of the program we went through a handout and the last problem we did on the handout was this:
Given the circuit below find the current through R3.
To solve I went through voltage drops in  2 loops, and I wrote a constrain equation for the bottom junction.

 

20I1+10R3=15

5I2-10R3=7

I1-I2-I3=0

 

 

so I3= -0.186A