First lets solve for x we know 3x=90. In this case x=30. Now we can solve for y. We know the triangle needs to equal 180 so y+2(30)=180. So we get y=120. Hope it helps
$15 more, than twice Friday's earnings
d is how much he earned on Friday
s is how much he earned on Saturday
2d + 15 = s

Is how you would solve this.
~ Hope this helps :)
Answer:
a) x = 10
b) x = -40
c) x = 10, -40
Step-by-step explanation:
a)

Taking 10 to the right hand side 10 becomes positive

So x = 10
b)

Taking 20 to the right hand side 20 becomes negative

Multiplying both sides by 2

So, x = -40
c)

Hence, x = 10, -40
So, two solutions can be provided