# Learn Interfaces by Building an Equation Solver - Step 25

### Tell us what’s happening:

Help me!
I had unpack the coefficients of the equation class and assign them to the variable a and b by method .values()
Why it doesnt work

``````from abc import ABC, abstractmethod

class Equation(ABC):
degree: int

def __init__(self, *args):
if (self.degree + 1) != len(args):
raise TypeError(
f"'Equation' object takes {self.degree + 1} positional arguments but {len(args)} were given"
)
if any(not isinstance(arg, (int, float)) for arg in args):
raise TypeError("Coefficients must be of type 'int' or 'float'")
if args[0] == 0:
raise ValueError("Highest degree coefficient must be different from zero")
self.coefficients = {(len(args) - n - 1): arg for n, arg in enumerate(args)}

def __init_subclass__(cls):
if not hasattr(cls, "degree"):
raise AttributeError(
f"Cannot create '{cls.__name__}' class: missing required attribute 'degree'"
)

def __str__(self):
terms = []
for n, coefficient in self.coefficients.items():
if not coefficient:
continue
if n == 0:
terms.append(f'{coefficient:+}')
elif n == 1:
terms.append(f'{coefficient:+}x')
equation_string = ' '.join(terms) + ' = 0'
return equation_string.strip('+').strip('+')

@abstractmethod
def solve(self):
pass

@abstractmethod
def analyze(self):
pass

class LinearEquation(Equation):
degree = 1

# User Editable Region

def solve(self):
coefficient = [i for i in self.coefficients.values()]
a = coefficient[0]
b = coefficient[1]
x = -(b/a)
return x

# User Editable Region

def analyze(self):
pass

lin_eq = LinearEquation(2, 3)
print(lin_eq)

``````

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