Question

Solve the equation using mental math.

$36=-4a$

Short answer

Value of given equation is $a=-9$.

Step-by-step solution

Step-1- Think provided equation as question in words

$36=-4a$

The question will be as:

What number need to multiply with -4 so that it becomes 36?

Hence answer for above question is -9.

Step-2- Checking our answer is correct or not 

Substitute $a=9$in given equation $36=-4a$.

$\begin{array}{c}36=-4a\\ 36=-4(-9)\\ 36=36\end{array}$

Step-3- Conclusion

Therefore, as both sides of above expression are same, the value of given equation is $a=-9$.