Please someone help me out and explain so I can understand better

What expression is equivalent to 1/2(2+3x-6)

Which of the following pair(s) of circles have las a common external tangent? select all that apply. a and b a and c b and c

The table below shows the approximate masses of a dust particle and a grain of pollen. dust particle 0.000000778 g grain of pollen 0.00000000155 g the mass of a dust particle can be estimated and written in the form a × 10^b, where a = 8 and b = the mass of a grain of pollen can be estimated and written in the form a × 10^b, where a = 2 and b = based on the estimates, the mass of a dust particle is approximately blank times larger than the mass of a grain of pollen.