The height , in feet, windowsills in a high-rise building is represented by this sequence: 3,15,27,39,...

Each windowsill goes up by a factor of 12 feet, so the next numbers are 51, 63, 75(feet) and so forth

Step-by-step explanation:

3, 15, 27, 39

3+12= 15

15+12= 27

27+12= 39

39+12= 51

51+12= 63

63+ 12= 75

x is variable or an unknown value to find

example:

2x = 5 which means x = 3