How do you write 1,400 in scientific notation

During a bike challenge riders have to collect various colored ribbons each 1/2 mile they collect a red ribbon each eighth mile they collect a green ribbon and each quarter mile they collect a blue ribbion wich colors of ribion will be collected at the 3/4 markrer

25 ! the line of best fit is h = 5a + 86. predict the height at age 16.

What does x = in this equation x+3+2x=x+5