At 18 a person has reached their [совершеннолетие] and can vote and drive a car.

Hint: A legal term is appropriate here.

majority

Info: ”Adulthood” is a more general term.

By 2003, Venus Williams was [последовательно] able to beat high-ranking challengers.

consistently

Info: Note that “consequently” means ‘as a result of (sth)’.

Einstein was primarily a dyed-in-the-wool [теоретик] , but his ideas have in fact turned out to be testable.

Hint: ”Dyed-in-the-wool” means ‘deeply, thoroughly’

theorist theoretician

Info: ”Theorist” is much more common than “theoretician”.

Finally, a plastic bag that is [для окружающей средыfriendly] !

Hint: A hyphen is usually appropriate if you make this a compound.

environment- environment environmentally

Info: Note that the adverb “environmentally” doesn’t have the hyphen.

Their complaints are actually off [цель] .

Hint: This is an idiom: “to be off…”

target