A number added to 9/7 is 13/5. What do you get when 13/5 is added to the number?
13/5 9/7 [OP_SUB] 13/5 [OP_ADD]
var_a = 2.6
var_b = 1.2857142857142858
var_c = var_a - var_b
var_d = 2.6
var_e = var_c + var_d
print('{:.2f}'.format(round(var_e+1e-10,2)))