Question 252547
This is a system of linear equations. Usually, you can subtract down or use some kind of multiplication and get the answer directly. In this case, we cannot.
(i) {{{1x + 2y = 11}}}
(ii) {{{3x + 1y = 13}}}
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step 1 - multiply (ii) by -2.
(iii) {{{ 1x + 2y =  11}}}
(iv)  {{{-6x - 2y = -26}}}
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step 2 - add down to eliminate the y.
(v) {{{-5x = -15}}} - -> X = 3.
If X = 3, then y = 4 and (X + Y) = 7.