Ecuaciones del tipo a + x = b, ax=b y ax + b = c

x + 23 = 72

22.5 + y = 72

 $\frac{4}{20}\ +\ x\ =\ \frac{20}{20}$  

c + c = 25

2x + 5x = 490

5x + 6x = 110

2x + 20 = 34

25 + 4y = 41

2x + 2x + 5x + 20 = 830

x - 25 = 70