Here you go, hope it isn't messy
25% decrease because if you multiply 20x.25 you get 5 and you minus the 5 from 20 books and you get 15 books
Solving for y, we add 5y to both sides and subtract 4, getting 9x-4=5y. Dividing both sides by 5, we get 9x/5-4/5=y. Since the slope is 9/5 (since 9/5*x=9x/5), we multiply it by -1 and find the reciprocal of it to get -5/9 as the perpendicular slope, so -5x/9+b=y. Plugging 1 in for x and -6 in for y, we get -5*1/9+b=-6 and by adding 5/9 to both sides we get -5-4/9=b , and since in y=mx+b y and x are variables, we end up with y=-5x/9+(-5-4/9) for slope intercept form.
To get it into standard form, we need it in ay+cx=b with a, b, and c being constants. Adding 5x/9 to both sides, we end up with y+5x/9=(-5-4/9) for standard form
There are 4 rules for congruent triangles:
SSS-->This means side,side,side and to prove triangles are congruent with this rule, all the sides will be the same on both triangles.
SAS-->This means side,angle,side and to prove triangles are congruent, you must have 2 sides and an angle the same on both triangles, but the angle MUST be in between the 2 sides.
ASA-->This means angle, side, angle and to prove triangles are congruent with this rule, you must have two angles and a side the same, but the side MUST be in between the two angles.
RHS-->This means right angle, hypotenuse, side and to prove triangles are congruent with this rule, you must have a right angle in both triangles, and have an equal hypotenuse and side.
Hope this helps:)
