The unknown number of the given expression is 8
Linear equations
Let the unknown number be x such that three times the sum of some number plus 3 is equal to 7 times the number minus 23 is expressed as;
3(x + 3) = 7x - 23
Expand
3x + 9= 7x - 23
Collect the like terms
3x-7x = -23 - 9
-4x = -32
x = 8
Hence the unknown number of the given expression is 8
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