solve the simultaneous equations : 3a+2b=7 and a-2b=5

Question

struggling to answer that question please help

Answer 1

Absolutely no need to struggle!

Just add those two equations together; the result will be one equation involving a, and you'll soon figure out what "a" is.

Then replace a in either of the original equations, and solve for b.

 

Answer 2

For this kind of questions, we have to find out the interrelationship between a and b. From the equation of a-2b=5, we can know that a=2b+5 and this is the relationship between a and b. Therefore, we can replace value a by using the term of (2b+5) into the first equation and get a new equation of 3*(2b+5)+2b=7. By solving this new equation, we can figure out that b is (-1), and a should be 3.