Answer:2\sqrt(5)+9\sqrt(7)
Explanation:
2\sqrt(20)-3\sqrt(7)=4\sqrt(5)-3\sqrt(7)
4\sqrt(5)-3\sqrt(7)-2\sqrt(5)=2\sqrt(5)-3\sqrt(7)
2\sqrt(5)-3\sqrt(7)+4\sqrt(63)=2\sqrt(5)+9\sqrt(7)
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