X+y=7
2x-y=5
Using substitution

x

=

2

y

=

3

Step-by-step explanation:

You can re-arrange equation

x

+

y

=

5

to get

x

=

5

−

y

and then substitute this into the equation

2

x

+

y

=

7

to get

2

(

5

−

y

)

+

y

=

7

.

This can then be simplified to

10

−

y

=

7

and so

3

−

y

=

0

which means

y

=

3

.

Substitute

y

=

3

into

x

+

y

=

5

and you get

x

+

3

=

5

, therefore:

7 weeks

step-by-step explanation:

convert each fraction to the least common multiple of 20, so 3/4 = 15/20 & 1/10 = 2/20, then divide 15 by 2 and you get a little over 7, so the food will last 7 weeks.

-2 is the right