Answer :

[tex]8.7+5.8-3.1*1*2.3 = (8.7 + 5.8) - (3.1 * 2.3)[/tex]

[tex](14.5) - (7.13)[/tex]

[tex]7.37[/tex]
I'm assuming that 1*1 means 1 times 1 and not 1^1 so

8.7+5.8-3.1*1*2.3
pemdas so mutiplication first
-3.1*1*2.3=-3.1*2.3=-7.13 since opposite signs multiplied make negative
then addition subtraction
8.7+5.8-7.13
14.50-7.13
7.37