If 3a + 2b = 7 and 2a + 2b = 9 , what is the value of

Hey there :)

We have two equations:
3a + 2b = 7 
2a + 2b = 9

We need to solve simultaneously to find the values of a and b

eq.1    3a + 2b = 7
eq.2 ( 2a + 2b = 9 ) x -1  ) multiply by -1 to cancel 2b

  3a + 2b = 7
- 2a - 2b = -9         ( Add both together )
-------------------
   a = - 2 

Substitute the value you found for a in a in order to find b

3( - 2 ) + 2b = 7                                                     2( - 2 ) + 2b = 9 
- 6 + 2b = 7                                    OR                  - 4 + 2b = 9
2b = 13                                                                   2b = 13        
b = [tex] \frac{13}{2} [/tex]                                                                 b = [tex] \frac{13}{2} [/tex]