Hello There!
The answer would be "23"
When we have an expression like this, the "x" next to a number means that we multiply the number next to the variable by it.
In this case, if "x" equals 4, then we multiply 5 by 4 and we get a product of 20 and we add 3 to get a sum of 23.
Have A Great Day!
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TheBlueFox