28 first graders and 12 other students attended a school assembly what percentage of the students at the assembly were first graders​

70%

Step-by-step explanation:

Find the total students who attended a school assembly:

28 + 12 = 40

100% = 40 students

1% = 40 ÷ 100 = 0.40

28 ÷ 0.40 = 70

70%

Step-by-step explanation:

28+12= 40

28/40= 0.7

0.7x100= 70

option 3 . (5x + 1) - (-10x + 6)

step-by-step explanation:

option 1 :

(4x + 3) + (-9x + 4)

or 4x+3 -9x + 4

or -5x + 7

option 2

(x - 2) - (6x - 9)

or x-2-6x + 9

or -5x + 7

option 3

(5x+ + 6)

or 5x + 1 + 10x -6

or 15x -5

option 4

-4x+2x+7-3x

-7x + 2x + 7

-5x + 7

hence only option 3 did   not satisfy the given simplify expression.