Question 972441
let xy be the two digit number, now
xy = 10x + y and
x - y = 3 then
x = y+3
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7(xy) = 4(yx)
7(10x+y) = 4(10y+x)
now substitute y+3 for x
7(10(y+3)+y) = 4(10y+y+3)
7(10y+30+y) = (40y+4y+12)
77y+210 = 44y+12
33y = -198
y = -6
x = -3
xy = -36
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check answer
7(-36) = 4(-63)
-252 = -252
answer checks