Wangari plants 12 trees every 3 hours, so her planting rate is 12 trees per 3 hours, or 4 trees per hour.
To find the equation that relates the number of trees Wangari plants (p) and the time she spends planting them (h) in hours, we can use the formula for direct variation:
p = k*h
where k is a constant of proportionality. Since Wangari plants at a rate of 4 trees per hour, k = 4:
p = 4h
Therefore, the equation that relates the number of trees Wangari plants (p) and the time she spends planting them (h) in hours is p = 4h.