BTGmoderatorDC wrote:If 5x + 3y = 17, what is the value of x?
(1) x is a positive integer
(2) y = 4x
OA B
Source: Official Guide
$$5x + 3y = 17\,\,\,\left( * \right)$$
$$? = x$$
$$\left( 1 \right)\,\,x \ge 1\,\,{\mathop{\rm int}} \,\,\,\left\{ \matrix{
\,{\rm{Take}}\,\,\left( {x,y} \right) = \left( {1,4} \right)\,\,\,\,\, \Rightarrow \,\,\,\,\,? = 1\,\, \hfill \cr
\,{\rm{Take}}\,\,\left( {x,y} \right) = \left( {4, - 1} \right)\,\,\,\,\, \Rightarrow \,\,\,\,? = 4\,\, \hfill \cr} \right.$$
$$\left( 2 \right)\,\,y = 4x\,\,\,\,\mathop \Rightarrow \limits^{\left( * \right)} \,\,\,\,5x + 3\left( {4x} \right) = 17\,\,\,\,\, \Rightarrow \,\,\,\,\,x\,\,\,{\text{unique}}\,\,\,\, \Rightarrow \,\,\,\,{\text{SUFF}}.\,\,\,\,$$
This solution follows the notations and rationale taught in the GMATH method.
Regards,
Fabio.
