No Podemos abrir su foto :c
Multiply all the terms by the same value to eliminate fraction denominators
a/9=-4
9 . a/9=9(-4)
The dot means multiplication
Then simplify to simplify cancel the multiplied terms that are in the denominator
a=9 . -4
Multiply the number
9 . -4 =36
And don’t forget to add the negative sign so the answer is
a= -36
Let x be the percent of p asked
then
m% of n = x% of p
m/100*n = x/100*p
mn = xp
x = mn/p
Unsure what you mean by diagonal right triangle
but if you wanted to find the hypothenuse (longest side) of a right triangle, you can apply pythagorean theorem

where c is the hypothenuse
a and b are the other sides