The 21st term of an AP is 13 and the sum of the first 21 term is 96 find the first term

What is the measure of angle 1? a.28 b.152 c.168 d.64

Find the solution to this system 2,1 1,-2 1,2 -1,2

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.