Name: David Dean
Who is asking: Other
Level: All

Question:
2a + 1b = 3.39 3a + 3b = 6.59
What formula do I use to find what a = ?

Hi David,

Not a formula but I can show you a process that you can use. One way to find a is to find a way to eliminate b. In the first equation the coefficient of b is 1 and in the second equation the coefficient of b is 3. Hence, if you multiply both sides of the first equation by 3 then, in both equations, the coefficient of b will be 3. The equations are

2a + 1b = 3.39
3a + 3b = 6.59

 
and multiplying the first equation by 3 gives
 
6a + 3b = 10.17
3a + 3b = 6.59

Subtracting the second equation from the first equation gives

3a = 3.58

Solve for a.

Cheers,
Harley
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