Please look at the pic and help it got marked wrong

Cumulative examcumulative exam active13time remaining02: 44: 18the graph represents the data cost for monthly internetservice for a cell phone. which function, c(x), represents the monthly cost in dollarsin terms of x, the number of gigabytes used in a month? cell phone internet service(15,5x + 10150,0sx522 < x < 664x115, osx< 25x + 20, 2< x< 650, 65815%,monthly cost (s)20x + 5| 50x,0 < x < 22 < x < 664x( 15x, osx< 2c(x) = 5x + 10, 2< x< 6150x, 65 x5+1234 5 6 7 8 9 10 11 12gigabytes used

Explain how you do each step what term makes it inconsistent y=2x - 4 ?

Complete the solution of the equation. find the value of y when x equals to 28 x+3y=28