A student got 20 out of 25 full marks and another student got 35 out of 50 full marks. Express their marks in fraction

20/25 = 4/5 for first student
35/50 = 7/10 for second student

Student 1 = 20/25

               = 4/5 (divide the denominator and numerator with 5)

Student 2 = 35/50

                 = 7/10 (divide the denominator and numerator with 5)

I wrote them in their lowest form. I hope you understood :)

The given piecewise function is
f(x) = 3 - x,          x<1
     = ax² + bx,  1 ≤ x < 2
     = 5x - 10,    x ≥ 2 

Part 1:
If a = 2  and b = 3
f(1⁻) = 3 - 1 = 2⁻  (approaching 2)
f(1) = 2(1²) + (3)(1) = 5
Because, f(x) is not continuous at x = 1

f(x) is not continuous.

Part 2:
In order for f(x) to be continuous at x=1, we want f(1) = 2.
That is,
a + b = 2    

a + b = 2

Part 3:
In order for f(x) to be continuous at x = 2,
5*2 - 10 = 0, therefore
4a + 2b = 0
2a + b = 0

2a + b = 0

Part 4:
For f(x) to be continuous at x=1 and at x=2 requires that
a + b = 2         (1)
2a + b = 0      (2)

Subtract (1) from (2):
a = -2
b = 2 - a = 4

a = - 2 and  b = 4

Part 5:
A graph of f(x) with a = -2 and b = 4 is shown below.

Note:
Although f(x) is continuous piecewise, it is not continuous in a mathematical sense.