6a+3b =6
2a +4b =5
solve it by elimination method

6a+3b=6       - - - - 1
2a+4b=5       - - - - - 2
_________

multiply equation  2   by 3

6a+3b=6
6a+12b=15
(-)   (-)    (-)
___________

    -9b = -9

b=-9/-9
b=9/9
b=1   
substitute  b=1  1n equation 1
  6a+3*1=6
 6a+3=6
6a =3
a=3/6
a=1/2