the letters are the numbers on a clock u have to decode them basically
x-C/D=H/A
x-15/20= 40/5
now multiple the numerator and denominator on x-15/20 by 20 to eliminate it from the bottom and to move it to the top to make it a single piece
x-15×20= 40/5 also to make it simple combine like terms aka -15×20. and simplify 40/5
x-300= 8 now add 300 on both sides to get x alone.
x-300+300=8+300
x=308 is your answer!