How do I do this please give a explanation
No links please ​

1/2a-4b

Step-by-step explanation:

When combining like terms you can only combine numbers with the same variables.

So we subtract 3/4a-1/4a=1/2a

And then we subtract the b values

2b-6b=-4b

1/2a-4b

the sum of all the angles in a triangle are equal to 180

so you can add   the 3 given angles together to equal 180:

5y + 2y + 2y = 180

or since all three angles have the same letter, combine the 3 angles to equal 180:

9y = 180