head start an earlier start 20. in over one's head taking on a task that you can't handle take care of, watch in order to protect try to be cheerful 21. keep an eye on 22. keep one's chin up 23. learn by heart, know by heart 24. let one's hair down memorize r...
Substitution method is one of the simplest way to solve systems of linear equations. This method works by simply finding the value of x-variable in terms of y-variable, then replacing the value of x-variable in the second equation. In order to use the substitution method, we follow the st...