Which set of coefficients would balance the following chemical equation?

H3PO4 + RbOH → H2O + Rb3PO4

First lets do Rb ... we have 1 one the left and 3 on the right. so 3RbOH will balance that

PO4 is equal on both side

since we put 3 for RbOH now we have 3 O on the left

so we put 3 for H2O

now we have 6 H on each side so everything is balanced