I think the answer would be 1.
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Well knowing these are both obtuse angles of the same shape and size we can begin. were looking to show AC is equal to DF we start by connecting A to C. A goes to C and makes this half an Oval shape along the bottom line now try connecting A to B and C to B AB and CB are not the same as AC and since these angles are the same shape and size we know DF should do the same so now we connect D to E and F to E similar to AC they do not match nor do they match AC itself leaving us to compare D to F after we do this we see that it creates the same sized half an oval as AC showing us that they are equal. :)
Since there are two negative symbols your answer will be positive. Your answer is 57.5
P: Parenthesis
E: Equation
M:Multiplication
D: Division
A : addition
S: Subtraction
So first you need to divide because it is before so you divide 18 by 6 which is 3 then you subtract (31 - 3) which gives you 28
answer : 28