Find the sum or difference of (-1)+(-8) please

Kathy spent 5/8 of her money on books and another 1/6 of her money on stationeries.what fraction of kathy’s money was left?

Maria walks a round trip of 0.75 mile to school every day.how many miles will she walk in 4.5 days

A33 gram sample of a substance that's used to detect explosives has a k-value of 0.1473. n = noekt no = initial mass (at time t = 0) n = mass at time t k = a positive constant that depends on the substance itself and on the units used to measure time t = time, in days