Question

a)
$2x + y = 7 \\3x - y = 8$
b)
$2x + 2y = 10 \\ 4 x + y = 15$
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Answer 1

$\left \{ {{2x+y=7} \atop {3x-y=8}} \right.\\\\2x+y=7\\y=7-2x\\\\3x-y=8\\\\3x-1.(7-2x)=8\\3x-7+2x=8\\5x-7=8\\x=\frac{15}{5} \\x=3\\\\2x+y=7\\2.(3)+y=7\\6+y=7\\y=7-6\\y=1\\\\(x, y)= (3, 1)\\\\\\b)\left \{ {{2x+2y=10} \atop {4x+y=15}} \right. \\\\4x+y=15\\y=15-4x\\\\2x+2y=10\\2x+2.(15-4x)=10\\2x+30-8x=10\\-6x+30=10\\-6x=10-30\\-6x=-20\\6x=20\\x=\frac{20}{6}\\x= \frac{10}{3} \\\\4x+y=15\\4.(\frac{10}{3})+y=15\\\frac{40}{3}+y=15 \\y=15-\frac{40}{3}\\y=\frac{5}{3}$

b) (x, y) = (10/3, 5/3)