i need help on this question

Answer:
Step-by-step explanation:
It would be answer b, because if you were to solve this, then this is how you would do it (in the most effecient way):
2.5x + 1.2 = 1.2x + 4.2
2.5x + 1.2 - 1.2 = 1.2x + 4.2 - 1.2
2.5x = 1.2x + 3
2.5x - 1.2x = 1.2x - 1.2x + 3
1.3x = 3
1.3x/1.3 = 3/1.3
x = 3/1.3