**Problem / Question**

**Introduction**

This
question was from a Facebook group not dedicated to “Singapore math”. The thing is, mathematics is really
an international experience, especially with modern social media.

Simultaneous equations can pose a challenge to students, but this one is
absolutely more challenging, because of the

*absolute value*.**The Absolute Value**

**Strategy**

The problem
is: we do not know whether each of

*x*and*y*is negative or otherwise. That potentially raises complications. There seems to be 4 cases to check. However, by making assumptions [H08] separately and checking for contradictions [H07], we can narrow down the possibilities. [H10] Finally, we can simplify the problem to a regular pair of simultaneous linear equations [H10] and solve it by the method of elimination. [H10, H11]**Solution**

H04. Look for pattern(s) [deciding what to eliminate]

H07. Use guess and check [is

*x*negative? is*y*negative?]
H08. Make suppositions [is

*x*negative? is*y*negative?]
H10. Simplify the problem

H11. Solve part of the problem

H13* Use Equation / write a
Mathematical Sentence

**Suitable Levels**

*****Lower Secondary Olympiad

*****GCE ‘O’ Level Additional Mathematics, “IP Mathematics” (challenge)

* other syllabuses that involve simultaneous
equations and absolute values

* any precocious or independent learner who
wants his/her mind tickled

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