I need help on all three please help thank you

In a sale there is 25% of all prices a chair costs £45 in sale how much was it before the sale

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.

Find the slope of the line that passes through the points (0, 0) and (-2, -3). 2/3 3/2 -3/2