Question 1120047
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<pre>
L = 3y + 9               (1)
L+14 = 2*(y+14) + 6.     (2)


Substitute (1) into (2). You will get


(3y + 9) + 14 = 2*(y+14) + 6

3y + 23 = 2y + 28 + 6

y = 28 + 6 - 23 = 11.


<U>Answer</U>.  The son is 11 years old.  The father (=Lucas) is 3*11 + 9 = 42 years old.
</pre>

Solved.


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<U>Be aware</U> : &nbsp;&nbsp;The system written by @josgarithmetic 


{{{system(L=3y+9,L+14=2y+6)}}}


is &nbsp;&nbsp;<U>I N C O R R E C T</U>.