if you are 6 ft tall and cast a 90" shadow and are standing 70" from a lamp how tall is the lamp

Answer 1

since 6' = 72 inches, if the lamp is x inches tall,

x/(70+90) = 72/90
x = 128

Answer 2

can you further explain the part where you stated...

x/(70+90)=72/90

when I take 72/90 I get .8
I must be missing something here...

Answer 3

draw a diagram. Two ratios are the same

lamp height:distance to shadow tip
person height:length of shadow

so,
x/160 = .8
x = 128