Keeping Od, this is the solution:
x + y = 2
2x + 7y = 9
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Step 1: Let's isolate x in equation 1, as follows:
x + y = 2
x = 2 - y
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Step 2: Let's substitute x and solve for y in equation 2, this way:
2x + 7y = 9
2 (2 - y) + 7y = 9
4 - 2y + 7y = 9
4 + 5y = 9
Subtracting 4 at both sides:
4 + 5y - 4 = 9 - 4
5y = 5
Dividing by 5 at both sides:
5y/5 = 5/5
y = 1
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Step 3: Let's substitute y and solve for x in the first equation, as follows:
x + y = 2
x + 1 = 2
Subtracting 1 at both sides:
x + 1 - 1 = 2 - 1
x = 1
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Step 4: Let's write the solution as an ordered pair, this way:
(1, 1)