8 x 7 = 56
Just multiply the two, if the question was 7 + 8 x 7
then you'd multiply 8 by 7 and that would give you 56
then you'd add 7 for the final answer of 63 but you don't have to add 7 in this problem
The discriminant is b^2-4ac
ax^2+bx+c=0
x^2+11x-10=0
11^2-4(1)(-10)
1. Simplify 11^2 to 121
121-4(1)(-10)
2. Simplify 4*1*-10 to -40
121-(-40)
3. Simplify brackets
121+40
4. Simplify
161
Your discriminant is 161
Check the picture below.

so.. the maximum point is at

and it happened after

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now, when the rocket reaches the ground, as you saw on the picture, y = 0, thus

"t" is an amount in seconds, for this specific phenomena, it cannot be negative, so -10 is not a feasible value.
I think that it is c or d but correct me if i am wrong