Let's solve this problem step-by-step:
[tex]7 * 9 = (7*10)-(7*x)[/tex]
- x: it is the delta in the equation given in your picture
We know (7*10) - (7*x) is equivalent to the 7*(10-x)
⇒ based on the Distributive Properties
[tex]a*(b+c) = ab + ac[/tex]
[tex]7*(10+(-x))=(7*10)+(7*(-x)=(7*10)-(7*x)[/tex]
So:
[tex]7*9=7(10-x)\\9=10-x\\x=10-9\\x= 1[/tex]
Thus delta (the little triangle in this problem) in this case is 1
Answer: 1
Hope that helps!
