(1/4+1/5)*х=1 целая 4/5

(1/4 + 1/5) * x = 1 4/5
(5/20 + 4/20) * x = 1 4/5
9/20x = 9/5
x = 9/5 : 9/20
x = 9/5 * 20/9
x = 4
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