It is really interesting.
I will assign symbol to each icon in the equation and solve as Linear algebra Problem :
Equation 1 : Lets assign symbol "A" to the sign
A+A+A=90, or 3A=90, or A=90/3, or A=30
Equation 2: Now we will assign symbol "B" to new icon of Arrow quiver:
A-B-B=20, (we already know A=30), so equation 2 becomes:
30-2B=20, or -2B=20-30, or -2B=-10, or B=10/2, or B=5;
Now for Equation 3, we assign symbol "C" for set of axe, Now we can see there is two set , also there is no plus (like equation 1) or minus sign (like equation 2) , that means they are not addition or subtraction , but they are Multiplication (as xx=x*x=x^2 , a common notation in math) , so we can write equation 3 as:
B+C*C=25
plugging the value of B=5
5+C*C=25, or C^2=25-5, or C= sqrt(20); (sqrt=square root); or C=4.472134 or C= - 4.472134 (approx);
(Indeed, sqrt(x^2)=+x as well as -x , both answer is true)
now for final equation , there going to be two answer and both are mathematically equally valid
For C= +4.472134
C-A*B= 4.472134-30*5= -145.527864 (approx)
For C= - 4.472134
C-A*B= - 154.472136
No one can explain it better :P
Now give me my 2000 Sapphires