What is the error in - 1.75+-1+4.25+3.75+1 + - 4.75+2=18.5

they don't respect the signs

Step-by-step explanation:

when you have a problem like the one above you have to put parentheses to the negative numbers either to add or subtract them, there is where the sign rule comes in

3.5

Step-by-step explanation:

-1.75 + (-1) + 4.25+3.75+1 + (-4.75) + 2

-1.75-1+4.25+3.75+1-4.75+2

-2.75+4.25+3.75+1-4.75+2

1.5+3.75+1-4.75+2

5.25+1-4.75+2

6.25-4.75+2

1.5+2

3.5