The total length of a road trip was 16.8 hours. If highway signs are posted every 0.6 hours, including one at the end of the road trip, how many highway signs will there be on the road trip? plz help

Can someone explain the elimination method to me for this problem?

3-12. write each answer with a reasonable number of figures. find the absolute uncertainty and percent relative uncertainty for each answer. (a) [12.41 (±0.09) + 4.16 (±0.01)] x 7.068 2 (±0.000 4) =? (b) [3.26 (±0.10) x 8.47 (±0.05)] - 0.18 (±0.06) =? (c) 6.843 (±0.008) x 104 + [2.09 (±0.04)- 1.63 (±0.01)] =?

One line passes through (-7,-4) and (5,4) . another line passes through the point (-4,6) and (6,-9)