Explanation:
2.3r - 7 + 6 = 21
2.3r - 1 = 21
2.3r = 22
r = 22/2.3
r = 9.6
2.3(4.23) - y + 6 = 21
9.73 - y + 6 = 21
15.73 - y = 21
-y = 5.27
y = -5.27
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