To find the answer, we just simply use PEMDAS, which means:
Parentheses
Exponents
Multiplication
(and/or)
Division
Addition
(and/or)
Subtraction
Solve the problem in this order. Since no operations are in the parentheses, we can skip that. The first operation we will do is multiplication. I can't really explain multiplication here, but you hopefully already know it, so multiply -4.31 by 3.09. Although there are negatives and decimals, treat it as a normal multiplication problem while doing the math.
This will give you -13.3179, just move the decimal point down, and since a positive is being multiplied by a negative, the answer is negative. Once you have this number, just add it to -0.98. This is the same as subtracting, since it is negative, so in other words, just subtract 0.98 from -13.3179, and you have your answer.
This would be -14.2979, or roughly -14.2.
Hope this helps! :)