Помогите решить уравнение:

4 * ( 250 : а + 12 ) = 68

Помогите решить плииз)) заранее спасибо!)

450: (18-y : 7) = 7*8-36: 6 

5*(810 : 9-x*3)=40*8-5 

Correct the mistakes/ 1/ I`ve lived in this street since six years/ 2/ Did Simon tidy his room yet?/ 3/ Clare has bought a new T-shirt yesterday/ 4/ Jenny has the same schoolbag for three years/ 5/ Jamie was in the football team since 2003/ 6/ I know Peter for two months/

огоньки - по частям слова