Well, 6/8 can be simplified: divide the numerator and denominator by 2, then your simplified fraction is 3/4. Now, multiply straight across: 4 times what=12? 3 does. So, you do the same thing to the numerator, because whatever you do to the denominator must be done to the numerator, and same reversed. 3*3=9, so the answer to this is 9/12!!
An isosceles triangle has 2 sides of the same length and one side that's not the same length.
So it says the shortest side, y, is 2.1m, so that means it's the side that is not the same length as the other two sides.
But the other two sides will be the same length. Let's make those 2 sides x.
The equation would be
x + x + 2.1 = 7.5
And with that you can find x.
3x + 2y + y - 3x = 180
3y = 180
y = 180/3
y = 60
3x = y - 3x
Let y = 60
3x = 60 - 3x
3x + 3x = 60
6x = 60
x = 60/6
x = 10
Answer: x = 10, y = 60