Thread: Linear equations addition

I'm probably making a silly mistake or Wolfram Alpha is lying to me.

Question: Find the value of c and d.




Rearranged, simplified and multiply each equation by 2:




Now find the common multiple which in my case I will use 12:




Then add them and find what d is worth:





Now when I plug this back into the equation, I will use the first one:







What am I doing wrong? Sorry if this is the long winded way to do it.

You aren't doing anything wrong, that solution is correct. Perhaps you entered the fraction incorrectly into Wolfram Alpha

You could have avoided one step and that is multiplying the first equation by 2.
Re arrange the equations and we have
2c + 3d = 13 ---- (1)
3c + d = 16 ------(2)
Multiply the second equation by -3 and re write the equations
2c + 3d = 13 ---- (1)
-9c -3 d = -48 ------(3)
Add the equations and you have:
-7c = -35 i.e., c = 5. Now get d from equation (2) we get d = 1