Ok i'm working in Amos Gilat Matlab guide 3rd edition, i'm doing problem 14 in chapter 4 and I'm not sure where to start

i have six equations and seven unknowns (a,b,c,d,e,f, and g) my equations are

a=d

a=e

b=f

3b=4e+f+g

c=2g

-b+c=2d-2e

the solutions are found by finding when all coefficients are positive by using a=1 as a guess and if that doesnt work moving on to a=2 and so on til they are all positive

help please