What is 5/6 + 3/7 as a mixed number

Which expression is equivalent to -5(3x - 6/7)

Ascientist has 50 grams of a radioactive element. the amount of radioactive element remaining after t days can be determined using the equation (1) after two days the scientist receives a second shipment of 50 grams of the same element. the equation used to represent the amount of shipment 2 remaining after t days is 10) - 50 which of the following is an equivalent form of the expression for the amount remaining in shipment 2? what’s the answer?

When i'm with my factor 5, my prodect is 20 .when i'm with my addend 6' my sum is 10.what number am i