Answer: +10 or 10 (you can just write the answer without the positive sign coz it'll be common to your teacher.)
Step-by-step explanation: The answer will be positive (+) because negative (-) multiplied by negative (-) is equal to positive (+). So, in this case, -2.5 * -4 is equal to positive 10 or 10.
I hope you guys get it. GOD BLESS!