'(2.2 + 4.7) + 3.8' is same as '2.2 + (4.7 + 3.8)'
True
We know that, instead of adding two numbers one after another, we need to only add their sum.
i.e., (x+y)+z=x+(y+z), for all numbers x,y and z.
Since the above is true for all numbers x,y and z, it must be true for x=2.2, y=4.7 and z=3.8.
So, (2.2 + 4.7) + 3.8 = 2.2 + (4.7 + 3.8)
Hence the given statement is true.