Solve the following pair of simultaneous equations: 1. 3x + 2y = 9 2. 6x + 5y = 21

We can solve this pair of simultaneous equations using substitution. To do this, we firstly have to rearrange one equation to get one variable on its own. For example, we can subtract 2y from each side of the first equation, and then divide both sides by 3 to obtain x = 3 - 2y/3. We then substitute x into equation 2 to obtain 6(3 - 2y/3) + 5y = 21. Simplifying and rearranging this, we obtain y = 3. We can then substitute this value of y into the equation x = 3 - 2y/3 to obtain x = 1.

Alternatively, we can use elimination. To do this, we must multiply one equation by a constant so that it has one variable with the same coefficient as the other equation. For example, by multiplying equation 1 by 2, we obtain 6x + 4y = 18. We see that our new equation and equation 2 have the same x coefficient. Thus, we subtract our new equation from equation 2, which gives y = 3. We can then substitute this value of y into one of our original equations and solve to obtain x = 1.