Tìm x a) x + (5621+ 1236) × 5 = 225690 b) x - 12 × 5 × 9 + 567= 1000

* Hướng dẫn giải

$\begin{array}{l}a)x+\left(5621+1236\right)\times 5=225690\\ x+6857\times 5=225690\\ x+34285=225690\\ x=225690-34285=191405\end{array}$$\begin{array}{l}b)x-12\times 5\times 9+567=1000\\ x-540+567=1000\\ x=1000+540-567\\ x=973\end{array}$

$\begin{array}{l}c)x+2+x+4+x+6+x+8=25760\\ (x+x+x+x)+(2+4+6+8)=25760\\ 4x+20=25760\\ 4x=25760-20\\ 4x=25740\\ x=25740:4=6435\end{array}$$\begin{array}{l}d)\left(6975-x+785\right):4=859\\ 7760-x=859\times 4\\ 7760-x=3436\\ x=7760-3436=4324\end{array}$