Which equations have one solution?

i need it fast

a)1/3x+3=26+6/18x-23

b)x+3+3x=-3+4x+6

c)2(1/5+1/4x-2x=x-1

d)4.3x+2.5-2.2x+2.2-2.1x=0

e)2(4x+3+2x=5(2x+3)

f)2/5x+10+3/5x=2x+5

Phyllis and chen are saving money to go to a football game. each friend starts with some money and saves a specific amount each week. phyllis made a graph to show the total she has saved at the end of each week. chen wrote an equation to show the total, y, he has saved at the end of each week, x. y = 15x + 15 compare the amount that each friend has when both friends start saving. select the correct answer from the drop-down menu to complete the statement. phyllis starts with $ and chen starts with $

Aman is 6 feet 3 inches tall. the top of his shadow touches a fire hydrant that is 13 feet 6 inches away. what is the angle of elevation from the base of the fire hydrant to the top of the man's head?

The square pyramid has a volume of 441 cubic inches. what is the value of x? 1/7x is the height x is the base