X+y=0 and x-y=10 solve by substitution.. how do i figure out the problem!

Question 3 of 30 paul buys fruit to make smoothies. he buys 3.78 pounds of apples, 2.12 pounds of peaches, and 4.45 pounds of oranges. paul rounds each weight to the nearest tenth of a pound. about how many pounds of fruit did paul buy? (a) 10.5 pounds (b) 10.2 pounds (c) 10.4 pounds (d) 10.0 pounds 30 points

Evaluate the expression for the given value of the variable 7a - 4a for a =8

What is the probability of throwing several dice with sum equal to 6 (six)? show the ways of possibilities for sum 6 (as the numerator) and the ways of throwing n dices for n = 1, 2, 3, 4 or 5 as denominator for all the questions to earn full credits. (a)throw one die, (b) throw two dice, (c) throw three dice (d) throw 4 dice, (e) throw 5 dice